DEPARTMENT OF PUBLIC HEALTH AND ENVIRONMENT 
Air Quality Control Commission  
REGULATION NUMBER 4 
Sale and Installation of Wood-Burning Appliances and the Use of Certain Wood-Burning 
Appliances during High Pollution Days 
5 CCR 1001-6  
[Editor’s Notes follow the text of the rules at the end of this CCR Document.]  
_________________________________________________________________________ 
I. DEFINITIONS 
A. Unless otherwise required by the context, as used in this Regulation: 
1. “Accredited Laboratory” means an independent testing laboratory that has obtained 
accreditation pursuant to the Federal Regulations 40 CFR Part 60 Subpart AAA (2015). 
2. (State Only) “Approved Masonry Heater” means a masonry heater as defined in Section 
I.A.12 that has complied with all requirements of Section IV. 
3. “Approved Pellet Stove” means a pellet stove as defined in Section I.A.18 that has 
complied with all the requirements of Section III. 
4. “Boiler” means a domestic solid wood-burning appliance used primarily for heating space 
where the appliance is located, by the distribution through pipes of a gas or fluid heated 
in the appliance. This appliance must be tested and listed as a boiler under accepted 
U.S. or Canadian safety testing codes. 
5. “Burn down time” shall mean that period of time not to exceed three hours following the 
declaration of a high pollution day required for the cessation of combustion within any wood-burning stove, pellet stove, masonry heater or wood-burning fireplace pursuant to 
this Regulation. 
6. REPEALED. 
7. “Cookstove” means a domestic wood-burning appliance that is designed primarily for 
cooking food and that has the following characteristics: 
a. An oven, with a volume of 1 cubic foot or greater, and an oven rack: 
b. A device for measuring oven temperatures; c. A flame path that is routed around the oven; 
d. A shaker grate; 
e. An ash pan; 
f. An ash clean-out door below the oven; and g. The absence of a fan or heat channels to dissipate heat from the appliance. 
8. “Dealer” means a person who sells wood-burning stoves, pellet stoves, wood-burning 
fireplaces or masonry heaters on a regular basis. 
8.5 “Exempt device” means a wood-burning device that does not meet the definition of a 
wood-burning stove by EPA standards (as contained in 40 CFR Part 60 Subpart AAA (2015)) and is not a fireplace, masonry heater, nor pellet stove as defined in this 
regulation. 
9. “Furnace” means a domestic solid wood-burning appliance that is designed to be located 
outside of ordinary living areas and is used for heating spaces other than the space 
where the appliance is located by the distribution through ducts of air heated in the 
appliance. The appliance must be tested and listed as a furnace under accepted U.S. or Canadian safety testing codes. 
10. “High pollution day” means those periods of time declared by Colorado Department of 
Public Health and Environment as provided for in Section 25-7-106.3(1), C.R.S. 
11. “Manufacturer” means a person who constructs a wood-burning stove or pellet stove or is 
engaged in the business of designing and constructing masonry heaters or wood-burning fireplaces. 
12. (State Only) “Masonry Heater” means an appliance designed for or capable or burning 
wood, capable of and intended for domestic space heating or domestic water heating, 
which meets the following criteria: 
a. A factory-built or site-built wood-burning appliance with a core constructed 
primarily of manufacturer-built, supplied or specified masonry materials (i.e., stone, cemented aggregate, clay, tile, or other non-combustible non-metallic solid materials) which weighs at least 800 kg; 
b. The firebox effluent of the masonry heater travels horizontally and/or downward 
through one or more heat absorbing masonry duct(s) for a distance at least the 
length of the largest single internal firebox dimension before leaving the masonry 
heater; 
For the purposes of this subparagraph: 
i. Horizontal or downward travel distance is defined as the net horizontal 
and/or downward internal duct length, measured from the top of the 
uppermost firebox door opening(s) to the exit of the masonry heater as traveled by any effluent on a single pathway through duct channel(s) within the heater (or average of net internal duct lengths for multiple 
pathways of different lengths, if applicable). Net internal duct length is 
measured from center of the internal side or top surface of a duct, horizontally or vertically to the center of the opposite side or the bottom surface of the same duct, and summed for multiple ducts or directions on 
a single pathway, if applicable. For duct channel(s) traversing horizontal 
angles of less than ninety degrees from vertical, only the net actual horizontal distance traveled is included in the total duct length. 
ii. The largest single internal firebox dimension is defined as the longest of 
either the length or the width of the firebox hearth and the height of the firebox, measured from the hearth to the top of the uppermost firebox 
door opening(s). 
c. The appliance has one or more air-controlling door(s) for fuel-loading that are 
designed to be closed during the combustion of fuel loads, and that control the 
entry of combustion air (beyond simple spark arresting screen(s)) to one or more 
inlet(s) as prescribed by the masonry heater manufacturer; 
d. The appliance is assembled in conformance with the underwriters' laboratories-
listed and/or manufacturer's specifications for its assembly and, if the core is constructed with a substantial proportion of materials not supplied by the manufacturer, is certified by a representative of the manufacturer to be 
substantially in conformance with those specifications. 
f. The appliance has a label permanently affixed to the appliance identifying its 
manufacturer and model. 
13. “Method 5G” and “Method 5H” are test methods for determination of particulate 
emissions from wood-burning heaters from dilution tunnel sampling and stack locations 
as described in 40 CFR, Part 60, Subpart AAA, Appendix A (2004). 
14. “Method 28” is a test method designed to establish certification test conditions and the 
particulate matter weighted emission values, as described in 40 CFR Part 60 Subpart 
AAA, Appendix A (2004). 
15. “Method 28A” is a test method to measure air to fuel ratios and minimum achievable burn 
rates as described in 40 CFR, Part 60 Subpart AAA, Appendix A (2004). 
16. “Model” means a group of wood stoves, pellet stoves, wood-burning fireplaces or 
masonry heaters that are identical to one another regarding design, emissions, and heating performance. 
17. REPEALED”New wood stove” means any wood -burning  stove other than one which was 
sold to an individual for personal use prior to January 1, 1987 . 
18. “Pellet Stove” means a heater which meets the following criteria: (1) the manufacturer 
makes no reference to burning cordwood in advertising or other literature, (2) the unit is 
safety listed for pellet fuel only, (3) the unit's operating and instruction manual must state 
the use of cordwood is prohibited by federal law, and (4) the unit must be manufactured and sold including a hopper and auger combination as integral parts. 
19. “Phase III Certified wood-burning stove” means a wood-burning stove that meets the 
emission standards set forth in Section II.A. 
20. “Primary source of heat” shall mean one or more residential wood-burning stoves, pellet 
stoves, masonry heaters or wood-burning fireplaces that provide more than half the 
annual heating demands for the residence. 
21. “Standard method” means the applicable testing procedures and criteria set forth in the 
Federal Regulations 40 CFR Part 60 Subpart AAA, Appendix A (2004). 
21.5 “Wood-burning appliance” means any stove, fireplace, masonry heater, furnace, fire pit, 
fixture or device used, or intended for use, to burn only clean, dry, untreated wood. 22. “Wood-burning fireplace” means an appliance with an open hearth (i.e. devoid of wood-
burning inserts, gas logs, or electric devices), is not a masonry hearer, may or may not be equipped with air-controlling doors, is primarily constructed of masonry materials 
(brick, stone or ceramic) and is installed in a dwelling or building for purpose of burning 
wood. 
23. “Wood-burning stove” means an appliance, primarily constructed of metal, designed for 
or capable of burning wood, including a fireplace insert, capable of and intended for domestic space heating or domestic water heating. 
II. LIMITATION ON THE SALE AND INSTALLATION OF WOOD-BURNING STOVES 
A. No person shall advertise to sell, offer to sell, sell, or install a  new  wood-burning stove in 
Colorado unless it has been tested, certified, and labeled for emission performance in 
accordance with applicable criteria and procedures specified in the Federal Regulations 40 CFR 
Part 60, Subpart AAA (2015) and meets the following emission standards. 
1. On or after July 1, 1988, no person shall advertise to sell, offer to sell, sell, or install a 
new wood-burning stove in Colorado unless it meets the emission standards set forth in 
40 CFR Part 60, Section 60.532(b)(1) or (2) (1988). 
2. On or after May 15, 2015, no person shall advertise to sell, offer to sell, sell, or install a 
new wood-burning stove in Colorado unless it meets the emission standards set forth in 
40 CFR Part 60, Section 60.532(a) (2015). 
23. (State Only) On or after May 15, 2020, no person shall advertise to sell, offer to sell, sell, 
or install a new wood-burning stove in Colorado unless it meets the emission standards 
set forth in 40 CFR Part 60, Section 60.532(b) or (c) (2015). 
B. The certification requirement shall apply to: 
1. Advertisements for sale and offers for sale communicated by any means to any person in 
Colorado, including, but not limited to, offers to sell or advertisements for sale that are mailed to any person in Colorado. 
2. Any sale occurring in Colorado, including, but not limited to, sales in which a new wood-
burning stove is shipped, delivered, or transported to any person in Colorado by a person 
located either inside or outside Colorado and to both the initial sale and any subsequent 
resale of a new wood-burning stove. 
C. Exemptions 
1. Exempt Devices, as defined in Section I.A.8.5 of this regulation. 
2. Boilers 3. Furnaces 4. Cookstoves 
D. On and after January 1, 1993 no person shall sell or install a used wood-burning device within 
those portions of the counties of Adams, Arapahoe, Boulder, Broomfield, Denver, Douglas, and 
Jefferson which are located in the AIR program area, as such area is defined in Section 42-4-
304(20)(a) (2006), C.R.S., unless it meets the requirements set forth in Section II.A. III. APPROVAL PROCEDURE FOR PELLET STOVES 
A. Before December 31, 2015, no person shall advertise to sell, offer to sell, sell, or install a pellet 
stove unless it has been designated as an approved pellet stove in accordance with this Sections III.A. through III.F. 
B. On or after August 1, 1992, a manufacturer of a pellet stove who wishes to have a particular 
model line designated as an approved pellet stove, shall submit to the Division for their review, 
the following information: 
1. test results showing an air to fuel ratio of 35:1 or greater, using Method 28A. 
2. test results using Method 5H, or Method 5G corrected to 5H, that have been conducted 
under minimum burn conditions, (category 1), Method 28. 
3. a one page letter signed by the laboratory president, verifying the information required in 
III.B.1. and 2. 
C. All tests conducted under II.B shall be performed by an accredited laboratory. 
D. Within twenty (20) working days after receipt of an application for approval, the Division shall 
notify the applicant if the application is complete. Within thirty (30) working days after receipt of a 
complete application, the Division shall notify the applicant whether the application satisfies all requirements for approval. 
E. If the Division denies approval, the Division shall notify the applicant in writing of the opportunity 
for a hearing before the Commission pursuant to Section 24-4-104(9), C.R.S. 
F. The Division shall grant approval if all information required by Section III A. is submitted and the 
test results in Section III.B.2. demonstrate particulate emissions do not exceed 4.1 grams per 
hour. 
G. On or after December 31, 2015, no person shall advertise to sell, offer to sell, sell, or install a 
pellet stove in Colorado unless it has been tested, certified, and labeled for emission performance 
in accordance with criteria and procedures specified in 40 CFR Part 60, Subpart AAA (2015) and meets the following emission standards: 
1. Until May 15, 2020, pellet stoves must continue to demonstrate that particulate emissions 
do not exceed 4.1 grams per hour. 
2. (State Only) On or after May 15, 2020, no person shall advertise to sell, offer to sell, sell, 
or install a wood-burning stove in Colorado unless it meets the emission standards set 
forth in 40 CFR Part 60, Section 60.532(b) or (c) (2015). 
IV. (State Only) MASONRY HEATERS 
A. Limitations on the installation and sale of masonry heaters – approval procedures 
1. No person shall advertise to sell, offer to sell, sell, or install a masonry heater in Colorado 
unless it has been designated as an approved masonry heater in accordance with this 
Section IV. 
2. A manufacturer or builder of a masonry heater who wishes to have a model or design 
designated as an approved masonry heater shall submit an application and test results 
that comply with the requirements of Appendix A. 3. Tests performed on masonry heaters shall comply with the particulates emission testing 
protocol set out in Appendix A and shall be performed by an accredited laboratory. The application shall include a letter signed by the laboratory president verifying: (1) the 
information required in Appendix A, and (2) that the methods used were conducted 
according to procedures contained in Appendix A. 
4. Within twenty (20) working days after receipt of an application for approval, the Division 
shall notify the applicant if the application is complete. Within thirty (30) working days after receipt of a complete application, the Division shall notify the applicant whether the 
application satisfies all requirements for approval. 
5. If the Division denies approval, the Division shall notify the applicant in writing of the 
opportunity for a hearing before the Commission pursuant to Section 24-4-104(9) C.R.S. 
6. The Division shall grant approval if all information required by Section IV and Appendix A 
is submitted, and the tested appliance is a masonry heater and test results do not exceed 
6.0 grams of particulate emissions per kilogram of fuel. 
7. The Division may grant approval for a masonry heater model that has not been tested if 
the untested model has substantially the same core construction as an approved model, 
and is substantially similar to the approved model in firebox and duct design, combustion function and probable emissions performance. The applicant must demonstrate that the 
untested model complies with the criteria and parameters set out in Appendix A for 
evaluating such similarity. The application must include all information required by Appendix A. 
8. Approved masonry heaters shall be labeled and equipped as provided in Appendix A. 
B.  Enforcement 
1. The Division may enter and inspect the property or premises of any manufacturer, or 
dealer, for the purpose of investigating any actual, suspected, or potential violation of this 
regulation; and may, at reasonable times, have access to and copy any document, inspect any masonry heater or testing equipment, or test the emissions of any masonry 
heater possessed by any manufacturer, or dealer, for the purpose of ascertaining 
compliance or noncompliance with this regulation. 
2. The Division shall also enforce the provisions of this regulation through all means 
authorized by Part 1 Title 25, C.R.S. 
C.  High Pollution Days 
1. Limitations on the use of wood burning appliances shall be applicable only in those 
portions of the counties of Adams, Arapahoe, Boulder, Broomfield, Denver, Douglas, and 
Jefferson are located in the AIR program area, as such area is defined in Section 42-4-
304(20)(a) (2006), C.R.S. but not including those areas above seven thousand feet elevation. 
2. Provisions of this section may be enforced by the appropriate local agency. Local 
agencies are encouraged to develop suitable enforcement programs and enter into an agreement with the State to promote more effective enforcement of this regulation. 
Approval of a masonry heater model pursuant to this regulation does not constitute 
authorization not to comply with requirements of any local ordinance or resolution relating to the installation or use of any masonry heater. 3. This section shall not apply within any municipality that had an ordinance mandating 
restricted use of masonry heaters on high pollution days in effect on January 1, 1990. All such exempt areas shall be required to submit a yearly report to the Commission no later 
than June 30, providing information concerning the enforcement actions pursuant to their 
ordinance for the previous heating season. 
4. No person shall operate a masonry heater during a high pollution day unless the 
appliance is exempt pursuant to Section IV.C.5. A burn down time shall be allowed for the burn down of existing fires prior to the initiation of enforcement action. The use of any 
fuel other than clean, dry, untreated wood in any masonry heater shall not constitute 
grounds for allowing its usage on a high pollution day. 
5. Exemptions 
a. Persons utilizing their masonry heater as a primary source of heat. 
b. Persons operating an approved masonry heater.   
V. ENFORCEMENT 
A. The Division may enter and inspect the property or premises of any manufacturer, or dealer, for 
the purpose of investigating any actual, suspected, or potential violation of this regulation; and 
may, at reasonable times, have access to and copy any document, inspect any wood-burning stove, wood-burning stove component, pellet stove, wood-burning fireplace or testing equipment, 
or test the emissions of any wood-burning stove, wood-burning fireplace, or pellet stove 
possessed by any manufacturer, or dealer, for the purpose of ascertaining compliance or noncompliance with this regulation. 
B. The Division shall also enforce the provisions of this regulation through all means authorized by 
Part 1 Title 25, C.R.S. 
VI. LIST OF APPROVED WOOD-BURNING APPLIANCES 
The Division shall request each dealer to make available to consumers a list of certified wood-burning 
stoves, exempt devices, approved pellet stoves and approved masonry heaters to be compiled by the Division. 
VII. HIGH POLLUTION DAYS 
A. Applicability 
Limitations on the use of wood burning appliances shall be applicable only in those portions of the 
counties of Adams, Arapahoe, Boulder, Broomfield, Denver, Douglas, and Jefferson are located 
in the AIR program area, as such area is defined in Section 42-4-304(20)(a) (2006), C.R.S. but not including those areas above seven thousand feet elevation. 
B. Provisions of this section may be enforced by the appropriate local agency. Local agencies are 
encouraged to develop suitable enforcement programs and enter into an agreement with the 
State to promote more effective enforcement of this regulation. Approval of a wood-burning stove, 
or pellet stove model pursuant to this regulation does not constitute authorization not to comply 
with requirements of any local ordinance or resolution relating to the installation or use of any 
wood-burning appliance. C. This section shall not apply within any municipality that had an ordinance mandating restricted 
use of wood-burning stoves, pellet stoves, and wood-burning fireplaces on high pollution days in effect on January 1, 1990. 
1. All such exempt areas shall be required to submit a yearly report to the Commission no 
later than June 30, providing information concerning the enforcement actions pursuant to 
their ordinance for the previous heating season. 
D. Prohibitions of use 
No person shall operate a stove, fireplace, furnace, fire pit, fixture or device used, or intended for 
use, to burn only clean, dry, untreated wood during a high pollution day unless the appliance is 
exempt pursuant to Section VII.E. A burn down time shall be allowed for the burn down of existing 
fires prior to the initiation of enforcement action. The use of any fuel other than clean, dry, untreated wood in any stove, fireplace, fire pit, fixture or device used, or intended for use, to burn 
only clean, dry, untreated wood shall not constitute grounds for allowing its usage on a high 
pollution day. 
E. Exemptions 
1. Persons utilizing their wood-burning stove, pellet stove, or wood-burning fireplace as a 
primary source of heat. 
2. Persons operating a certified wood-burning stove or wood-burning fireplace insert that 
meets the requirements in Section II. 
3. Persons operating an approved or certified pellet stove or pellet-burning fireplace insert 
that meets the requirements in Section III. 
VIII. REQUIREMENTS FOR INSTALLATION OF FIREPLACES 
A. On and after the January 1, 1993, no person shall install any fireplace in any dwelling in the area 
defined in Section  VIII.A VII.A . unless it is one of the following: 
1. a gas appliance. 
2. an electric device. 3. a fireplace insert that meets the requirements set forth in Section II.A. 4. an approved pellet burning fireplace insert that meets the requirements set forth in 
Section III. 
5. any other clean burning device approved by the Commission which meets the emission 
standard set forth in Section II.A. 
B. This section shall not apply to any municipality or a county, which has a provision in effect on 
January 1, 1993, which is substantially equivalent of this section as determined by the 
Commission. 
IX. IMPLEMENTATION OF LO CAL CONTROL STRATEGIES 
The local jurisdictions listed below shall implement and enforce the indicated ordinances and resolutions, 
as they exist on January 1, 1993. This ordinance limits wood-burning on high pollution days as 
determined by the Colorado Department of Public Health and Environment. In addition, each shall implement and enforce any ordinance adopted in accordance with this regulation. The indicated 
ordinances or resolutions may be amended in the sole discretion of the respective governing body, provided that they shall be submitted immediately to the Colorado Air Quality Control Commission and 
the United States Environmental Protection Agency as revisions to the State Implementation Plan. The 
listed ordinances and resolutions shall remain in full force and effect until such time as the jurisdiction obtains full approval of a State Implementation Plan revision.  
 
Community HPD 
Ordinance 
Number Date 
Enacted Construction 
Ordinance Date 
Enacted  
Arvada 2451 11/87   
Aurora 87-118 4/86 92/47 5/92 
Boulder 5007 10/86 5445 4/92 
Broomfield 794 11/88  . 
Denver Chapter 4.24 10/86 Chapter 4.24 5/90 
Douglas County   R-991-128 11/91 
Englewood 31 9/92 39 10/92 
Federal Heights 565 1/88   
Glendale 2 1/88 15 10/92 
Greenwood Village 17 6/88 9 3/92 
Jefferson County R-CC89-873 12/89 R-CC90-617 1/91 
Lafayette 24 11/88  7/93 
Lakewood 113 12/86 61 10/92 
Littleton 17 12/88 26 8/92 
Longmont 1 1/89   
Mountain View 5 1/91   
Sheridan 22 11/88 1 1/93 
Thornton 2120 10/91 2194 10/92 
Westminster 6/14 11/87 20 12/92 
X. REFERENCES Written statements of the basis and purpose of this regulation and revisions as well as all other material 
referenced in this Regulation is hereby incorporated by reference by the Air Quality Control Commission and made a part of the Colorado Air Quality Control Commission Regulations. Materials incorporated by 
reference are those referenced and do not include later amendments. The material incorporated by 
reference is available for public inspection during regular business hours at the Office of the Commission, located at 4300 Cherry Creek Drive South, Denver, Colorado 80246-1530. Parties wishing to inspect 
these materials should contact the Technical Secretary of the Commission, located at the Office of the 
Commission.  The material incorporated by reference is also available through the United States Government Printing Office, online at www.gpo.gov/fdsys . 
Regulation Number 4 - Adoption Chronology 
To set a standard test methodology, an emission standard developed, establish a certification fee, and 
develop an emission label - 
Adopted: June 27, 1985 
Effective: July 30, 1985 
Revised to raise the certification fee - 
Adopted: September 18, 1986 
Effective: October 30, 1986 
Revised to establish a definition for new woodstoves and exemptions from the woodstove certification 
program - 
Adopted: May 19, 1988 
Effective: June 30, 1988 
Revised to establish a woodstove certification program - 
Adopted: May 17, 1990 
Effective: June 30, 1990 
Revised to include provisions for pellet stoves – 
Adopted: August 20, 1992 Effective: September 30, 1992 
Revised to make locally adopted ordinances state enforceable - 
Adopted: June 24, 1993 
Effective: August 30, 1993 
Revised to include provisions for masonry heaters - 
Adopted: April 21, 1994 
Effective: June 30, 1994 Revised Section X to meet requirements for incorporation by reference - 
Adopted: February 16, 1995 
Effective: April 30, 1995 
Revised to update references to NSPS AAA and specify masonry heater provisions as State Only – 
Adopted:  November 19, 2015 
Effective:  January 14, 2016  
Revised to reinsert new wood stove definition – 
Adopted:  March 16, 2017 
Effective:  May 15 , 2017  
XI. STATEMENTS OF BASIS, SPECIFIC STATUTORY AUTHORITY AND PURPOSE 
A. Adopted:  November 19, 2015 
This Statement of Basis, Specific Statutory Authority, and Purpose complies with the requirements of the 
Colorado Administrative Procedures Act, C.R.S. § 24-4-103, the Colorado Air Pollution Prevention and 
Control Act, C.R.S. §§ 25-7-110 and 25-7-110.5, and the Air Quality Control Commission’s 
(“Commission”) Procedural Rules. 
Basis 
The Commission revised Regulation Number 4 to update definitions, emission standards, certification and 
labeling requirements, and citation references, for consistency with and as referenced in the revised 40 
CFR Part 60, Subpart AAA, Standards of Performance for New Residential Wood Heaters (“NSPS AAA”). 
The wood-burning and pellet stove requirements in Regulation 4 are part of Colorado’s Particulate Matter 
< 10 μg/m3 (“PM10”) and Carbon Monoxide (“CO”) State Implementation Plans (“SIP”). The masonry 
heater requirements in Regulation 4 are state-only provisions. 
Specific Statutory Authority 
The Colorado Air Pollution Prevention and Control Act, C.R.S. §§ 25-7-105(1)(b), 25-7-106(1)(c), and 25- 
7-109, authorize the Commission to adopt emission control regulations. Section 25-7-106(6) authorizes the Commission to require monitoring, recordkeeping, and reporting. And, Sections 25-7-401 through 413 
and 25-7-106.3 direct the Commission to promulgate rules and regulations for wood-burning stoves to 
reduce particulate and carbon monoxide emissions, including emission performance standards, testing criteria, labeling requirements, and certifications of performance standard.  
Purpose 
Regulation 4 sets particulate matter emission standards for wood-burning stoves, pellet stoves, and 
masonry heaters and prohibits the sale or installation of devices that do not meet the standards. For wood-burning stoves and fireplace inserts, Regulation 4 specifically references the testing, certification, and labeling requirements in the 1988 NSPS AAA. For pe llet stoves, pellet burning fireplace inserts, and 
masonry heaters, Regulation 4 requires testing by laboratories accredited according to the 1988 NSPS 
AAA. On March 16, 2015, EPA published revisions to NSPS AAA. Therefore, the Commission revised Regulation 4 for consistency with the revised NSPS AAA.  Formatted:  No underlineFor wood-burning stoves and fireplace inserts, th e Commission updated the NSPS AAA citation reference 
to require wood-burning stoves meet the testing, certification, and labeling requirements in the revised NSPS AAA. The Commission also revised the Regulati on 4 definition of wood-burning stove to 
correspond to the revised NSPS AAA definition of wood heater, upon which Regulation 4 relies. For pellet 
stoves, pellet burning fireplace inserts, and masonry heaters, the Commission updated the NSPS AAA citation reference in the definition of accredited laboratory to ensure that wood heater testing is conducted 
by laboratories accredited under the revised NSPS AAA. Some NSPS AAA citation references, such as 
Methods 5G, 5H, 28, and 28A, were not updated because those Methods are not referenced in the revised NSPS AAA. These revisions allow the continue d testing of pellet stoves and masonry heaters by 
referencing currently certified laboratories. These revisions also allow the continued sale and installation 
of wood-burning stoves because after the effective date of the revised NSPS Step 2 emission standard in 
2020, the wood-burning stoves allowed under Regulation 4 would no longer be available due to the revised testing, certif ication, labeling requirements in NSPS AAA. 
The Commission revised the pellet stove provisions to retain the current, more stringent emission 
standard of 4.1 g/hr in Regulation 4 for pellet stoves and to require pellet stoves sold or installed after the 
compliance date of the NSPS AAA Step 2 emission standard meet the future, more stringent NSPS AAA 2020 emission standard. The Commission also revised the pellet stove testing, certification, and labeling 
requirements for consistency with the testing, certif ication, and labeling requirements in the revised NSPS 
AAA.     
The Commission also clarified that masonry heater provisions are State Only. The Commission adopted 
the masonry heater provisions after Regulation 4 was included in Colorado’s PM10 and Carbon Monoxide 
State Implementation Plans (“SIP”). Therefore, the Commission specified the masonry heater provisions 
as State Only, thus not part of Colorado’s SIPs. As part of this clarification, the Commission duplicated 
the enforcement and high pollution day provisions, as related to masonry heaters, under the State Only 
masonry heater section.  
The Commission also made additional administrative revisions and corrected typographical, grammatical, 
and formatting errors. 
Findings of Fact 
The revisions to Regulation 4 do not exceed the requirements of the federal Clean Air Act or regulations 
because the revisions reference federal standards for wood heaters. The retention of the more stringent 4.1 g/hr emission limit for pellet stoves also does not exceed the requirements of the federal Act or 
regulations because that requirement is part of Colorado’s current, EPA approved SIP and federally 
enforceable. However, to the extent that these revisions could be viewed as exceeding or differing from 
the federal act, the Commission determines in accordance with C.R.S. § 25-7-110.5(5)(b): 
1. Residential wood heaters are subject to NSPS AAA, which establishes testing, 
certification, and labeling requirements, and emission standards for affected units. Regulation 4 references these requirements.    
2. NSPS AAA contains performance-based standards for wood heaters and is flexible with 
respect to designing wood heaters to meet the emission limits.   
3. Particulate matter emissions are of concern to Colorado. NSPS AAA will reduce 
particulate emissions from wood heaters. The retention of the 4.1 g/hr emission standard 
for pellet stoves currently in Regulation 4 will ensure that particulate matter emissions 
from affected pellet stoves do not increase until the more stringent NSPS AAA emission standard in 2020. Because the 2020 emission standards are not necessary for Colorado 
to demonstrate attainment with the PM10 or CO NAAQS, the Commission referenced the 
2020 emission standards in Regulation 4 but specified the 2020 emission standards as a 
State Only requirement.  4. NSPS AAA provides the wood heater industry with certainty and clarity by establishing 
standards, testing, certification, and labeling requirements for affected facilities.  
5. NSPS AAA allows manufacturers to sell their wood heater inventory through December 
31, 2015. NSPS AAA also automatically ext ends the certificatio n of wood heaters 
certified under the 1988 NSPS AAA, that also meet the revised NSPS AAA Step 1 
emission standard, until the compliance deadline for the revised NSPS AAA Step 2 
emission standard. And, EPA revised the laboratory accreditation requirements in NSPS AAA, which are referenced in Regulation 4 for the testing of pellet stoves and masonry 
heaters. If Regulation 4 is not revised, after December 31, 2015, Regulation 4 will only 
allow the sale and installation of wood-burning stoves that are currently certified under 
the 1988 NSPS and that meet the revised NSPS AAA Step 1 emission standard, and pellet stoves that follow the current Regulation 4 approval procedures. In addition, the 
pellet stove emission standard in Regulation 4 will be less stringent than the Step 2 
emission standard in the revised NSPS AAA. Further, if the NSPS AAA citation reference 
in Regulation 4 for accredited laboratories is not revised, Regulation 4 will require pellet 
stove and masonry heater testing by laboratories accredited under the 1988 NSPS AAA, a process that was revised in the 2015 NSPS AAA.    
6. The emission limits in NSPS AAA assist in establishing and maintaining a reasonable 
margin for accommodation of uncertainty and future growth. 
7. NSPS AAA and Regulation 4 establish reasonable equity in the requirements for various 
sources because affected wood heaters are subject to the same requirements.  
8. Failure to adopt the revisions would effectively prohibit the sale and installation of wood-
burning stoves in Colorado because the wood-burning stoves allowed under Regulation 4 
will no longer be available due to revised emission standard, testing, labeling, and 
certification requirements in NSPS AAA. Failure to adopt the revisions would also effectively prohibit the testing of pellet stoves and masonry heaters due to the revised 
laboratory accreditation requirements in N SPS AAA. And, retaining the 4.1 g/hr standard 
for pellet stoves will maintain the current emission reductions from affected pellet stoves.  
9. These revisions do not include procedural, reporting, or monitoring requirements that are 
different from applicable federal requirements. Affected pellet stoves will be able to show compliance with the retained 4.1 g/hr emission limit currently in Regulation 4 through the 
testing requirements in NSPS AAA. 
10. Demonstrated technology is available to comply with NSPS AAA and Regulation 4. 11. The revisions will contribute to further reductions of particulate emissions and therefore 
contribute to the prevention of pollution.  
12. An alternative rule could obtain the emission reductions to be achieved by NSPS AAA; 
however, referencing NSPS AAA in Regulation 4 is a simple, effective revision that will reduce particulate emissions from room heaters. A no action alternative would not 
address or achieve the emission reductions to be achieved through these revisions. 
Further, failure to adopt the revisions would effectively prohibit testing of pellet stoves and masonry heaters and the sale and installation of wood-burning stoves in Colorado 
because the wood-burning stoves allowed under Regulation 4 will no longer be available. 
As part of adopting the revisions to Regulation Number 4, the Commission has taken into consideration 
each of the factors set forth in C.R.S. § 25-7-109(1)(b). To the extent that C.R.S. § 25-7-110.8 requirements apply to this rulemaking, and after considering all the 
information in the record, the Commission hereby makes the determination that: 
1. These rules are based upon reasonably available, validated, reviewed, and sound 
scientific methodologies, and the Commission has considered all information submitted 
by interested parties. 
2. Evidence in the record supports the finding that the rules shall result in a demonstrable 
reduction of particulate emissions. 
3. Evidence in the record supports the finding that the rules shall bring about reductions in 
risks to human health and the environment that justify the costs to implement and comply 
with the rules. 
4. The rules are the most cost-effective to achieve the necessary reduction in air pollution 
and provide the regulated community flexibility. 
5. The selected regulatory alternative will maximize the air quality benefits of regulation in 
the most cost-effective manner. 
Further, these revisions will include any typographical, grammatical and formatting errors throughout the 
regulation. 
B. Adopted:  March 16, 2017 
This Statement of Basis, Specific Statutory Authority, and Purpose complies with the requirements of the 
Colorado Administrative Procedures Act, C.R.S. § 24-4-103, the Colorado Air Pollution Prevention and 
Control Act, C.R.S. §§ 25-7-110 and 25-7-110.5, and the Air Quality Control Commission’s 
(“Commission”) Procedural Rules. The Commission considered the requirements of C.R.S. § 25-7-110.8 
as part of this rulemaking. 
Basis 
The Commission revised Regulation Number 4 to reestablish a definition for new wood stove and clarify 
that the requirements for wood stove certification, testing, and labeling requirements are limited to new 
wood stoves state-wide and used wood stoves located in the defined Program Area.  These revisions 
provide consistency with 40 CFR Part 60, Subpart AAA, Standards of Performance for New Residential 
Wood Heaters (“NSPS AAA”), state st atute, and U.S. Environmental Protection Agency (EPA) approved 
language from Colorado’s Particulate Matter (“PM10”) and Carbon Monoxide (“CO”) State Implementation 
Plans (“SIP”). 
Specific Statutory Authority 
The Colorado Air Pollution Prevention and Control Act, C.R.S. §§ 25-7-105(1)(b), 25-7-106(1)(c), and 25- 
7-109, authorize the Commission to adopt emission control regulations. Section 25-7-106(6) authorizes 
the Commission to require monitoring, recordkeeping, and reporting. And, Sections 25-7-401 through 413 
and 25-7-106.3 direct the Commission to promulgate rules and regulations for wood-burning stoves to 
reduce particulate and carbon monoxide emissions, including emission performance standards, testing 
criteria, labeling requirements, and certifications of performance standard.  Specifically, CRS Section 25-
7-403(2)(a)(VII) requires the Commission to define new wood stove, whereas CRS Section 25-7-405.5 
limits the authority of the Commission to regulate the used wood stove certification, testing, and labeling 
requirements to the defined Program Area.  
Purpose Formatted:  par1, Indent: Left:  0", First line:  0", Tab stops:
Not at  0.5" +  1" +  1.5"
Formatted:  upar1, Tab stops: Not at  0.5" +  1"During a rule review process, the Commission determined that Regulation Number 4 did not include a 
required definition of new wood stove. Regulation Number 4 did define new wood stove until 2006, at 
which time the Commission repealed the definition for clarity. The definition of new wood stove caused 
confusion because Regulation Number 4 contained three different but related definitions for roughly the 
same devices, defining “new wood stove”, “wood burning stove”, and “certified wood stove”. With the 
2006 repeal of the definition of new wood stove, Regulation Number 4 instead relied on the 1988 
applicability date in NSPS AAA to define new wood stove. While these revisions were submitted to EPA 
for approval into Colorado’s SIP, these revisions were later withdrawn in full prior to EPA approval 
because “State Only” provisions for masonry heaters were included in the SIP revisions. The withdrawal 
means that the EPA approved version of Regulation Number 4, relied on in Colorado’s PM10 and CO 
SIPs, still includes the definitions of new wood stove and certified wood stove. 
Due to the statutory requirement to define new wood stove and for consistency with current EPA 
approved SIP language, the Commission has reestablished a “new wood stove” definition, clarified that 
wood stove testing, certification, and labeling requirements apply to new wood stoves state-wide and 
used wood stoves within the defined Program Area, and made related administrative revisions. 
These revisions to Regulation Number 4 do not exceed the requirements of the federal Clean Air Act or 
regulations because the revisions reestablish a federal definition for new wood stoves, and clarify existing 
federally approved wood stove testing, certification and labeling requirements found in Colorado’s PM 
and CO SIP such that they satisfy statutory authority to regulate wood stoves. No further analysis of 
C.R.S. § 25-7-110.5(5)(b) or : § 25-7-109(1)(b)or § 25-7-110.8 requirements was performed. 
APPENDIX A 
Test Method Protocols for Measuring Wood-Burning Masonry Heater Emissions 
Revision/Update: May 16, 2006 
1.0 SCOPE 
These Test Method Protocols comprise the Colorado Department of Public Health and Environment, Air 
Pollution Control Division (Colorado APCD) wood-burning masonry heater emissions performance requirements, masonry heater approval and certification procedures, Colorado APCD test-laboratory 
accreditation requirements, masonry heater manufacturer/builder record-keeping and reporting 
requirements, and test method protocols for measuring wood-burning masonry heater particulate 
emissions. 
2.0 DEFINITIONS 
Terms as used in these Test Method Protocols are defined as follows: 
Approved Masonry Heater - a masonry heater that has been certified by the Colorado APCD as 
meeting the requirements of Colorado APCD Regulation Number 4 and these Test Method 
Protocols. 
Burn Rate - the average rate at which test-fuel is consumed in a masonry heater during a test-
burn period; measured in mass of dry wood burned per hour (kg/hour, lb/hour). 
Calibration Drift - the difference in an analyzer reading from the initial calibration response at a 
mid-range calibration value after a stated period of operation during which no maintenance, 
repair, or adjustment took place. Formatted:  upar1, Tab stops: Not at  0.5" +  1"
Formatted:  upar1Calibration Error - the difference between the gas concentration displayed by a gas analyzer and 
the known concentration of the calibration gas when the calibration gas is introduced directly to the analyzer. 
Calibration Gas - a known concentration of carbon dioxide (CO 2), carbon monoxide (CO), and/or 
oxygen (O 2) in nitrogen (N2). 
Certification Test or Certification Audit Test - the completion of at least one, three-fuel-load test-
burn in accordance with the masonry heater operating protocols and the measurement and 
analysis procedures specified by these Test Method Protocols. 
Effective Flue-Gas Duct Diameter (ED) - for a round flue-gas duct the actual diameter. For a 
rectangular flue-gas duct it is determined using Equation 2.1 as follows: 
ED = (2 x (L x W)) / (L + W) Equation 2.1 
Where: L = Flue rectangular length. 
W = Flue rectangular width. 
Emissions Factor Margin - the difference between a passing emissions factor result for a masonry 
heater tested in accordance with these Test Method Protocols and the Colorado APCD 
Regulation Number 4 masonry heater emissions factor standard (See 3.1.2). 
Firebox - the chamber in the masonry heater within which fuel charges are placed and burned. Flue-Gas Exhaust Duct - the connector pipe, chimney, or other duct form that conveys exhaust 
gases from the masonry heater firebox to the outdoor atmosphere. Flue-gas exhaust duct cross-sectional area is calculated using duct dimensions measured at the narrowest point downstream 
from the horizontal plane which intersects the top most edge of the fuel loading door (See 
definition for "Firebox Height" under “Usable Firebox Volume”). 
Fuel-Elevating Grate - a non-combustible structure capable of elevating a fuel load above the 
hearth of a masonry heater while offering no, or very little impedance to the passage of 
combustion air supplies to the bottom of the fuel load and up through the fuel load. 
Fuel-Elevating Grate Height - the fuel elevation height above the hearth; the distance between 
the hearth and a horizontal plane at the bottom of an elevated fuel load. 
Fuel, Total Weight - the total weight of all fuel pieces in each fuel-load crib including the weight of 
all fuel-piece spacers. Total Test-Period Fuel Weight is the weight of all three fuel-load cribs plus 
the weight of the kindling used during the test. 
Hearth Dimensions 
Primary Horizontal Hearth Dimension (PH hd) - for all hearth shapes, the length of a line 
drawn within the hearth perimeter that is: 1) either a line of hearth plan-view symmetry or 
the longest line that can be drawn within the hearth perimeter perpendicular to a plan-view line of symmetry and 2) the axis parallel to which fuel-piece lengths are oriented for 
testing. The masonry heater manufacturer or builder shall designate the PH hd, choosing 
either a line of symmetry or the longest line that can be drawn perpendicular to a line of 
symmetry, whichever is to be the axis line along which fuel piece lengths are oriented in parallel for burning. Non-symmetrical hearth shapes - the PH hd shall be designated by the Colorado 
APCD in accordance with the objective of making fuel piece orientation reflect 
the basic length and width orientation of the hearth within the space intended for 
fuel placement and burning. 
Secondary Horizontal Hearth Dimension (SH hd) - for all hearth area shapes the length of 
the longest line that can be drawn within the hearth perimeter perpendicular to the 
designated PH hd. 
Multiple Lines of Symmetry - hearth shapes may have more than one line of symmetry to 
choose from. The SH hd associated with one PH hd and line of symmetry may not be used 
for calculating fuel crib dimensions with a PH hd based on a different line of symmetry. 
Note: For square and full-circle hearth shapes, the PH hd and SH hd are of equal length. 
Horizontal Flue-Gas Pathway - the total net horizontal-duct centerline distance measured from 
the point where the vertical centerline of the flue-gas exit duct from the firebox intersects the 
horizontal plane of the firebox height (See definition for "Firebox Height" under “Usable Firebox 
Volume”) to the point where the centerline of the exhaust duct exit to the atmosphere intersects 
the horizontal plane at the total vertical extent (i.e., height) of the exhaust duct at the flue-gas exit to the atmosphere. For the purpose, horizontal shall mean any amount of duct centerline traverse 
that is created by any angle that is either more or less than 90° or 270° from vertical. 
Internal Assembly - the core construction and firebox design factors that may affect a masonry 
heater’s combustion function or particulate emissions factor. 
Masonry Heaters - wood-burning devices which are exempt from Title 40 of the Code of Federal 
Regulations (CFR) Part 60, Subpart AAA (2015), are not cookstoves, boilers, furnaces, or pellet stoves as defined in 40 CFR Part 60, Subpart AAA (2015), follow the guidelines of E1602-03 Standard Guide for Construction of Solid Fuel Burning Masonry Heaters, and are distinguished 
from fireplaces by Colorado APCD Regulation Number 4. Masonry heaters are designed for 
operation only in a closed combustion chamber configuration. 
Masonry Heater Design - the construction and/or fabrication specifications including all 
dimensions and materials required for manufacturing or building a masonry heater. 
Masonry Heater Model Line - a series of masonry heater models which all have the same internal 
assembly. Each model in a model line may have different facade designs and external decorative features but must have the same internal assemblies. A masonry heater is deemed to have the 
same internal assembly if all internal assembly dimensions meet the criteria outlined in Section 
3.2.2.1 are within 3.0% of the Colorado APCD-approved masonry heater. 
Maximum Flue-Gas Carbon Dioxide Plus Carbon Monoxide Peak - the difference between the 
baseline air-supply CO 2 +CO concentration (normally 0) and the highest 5-minute average data 
point CO 2 +CO concentration measured and recorded during the burning of a test fuel charge. 
Maximum Flue-Gas Oxygen Depression - the difference between the baseline air supply oxygen 
concentration (i.e., 20.9%) and the lowest 5-minute average data point oxygen concentration 
measured and recorded during the burning of a test-fuel charge. 
Pre-Test Flue-Gas Temperature - the temperature measured at the flue-gas sampling and 
temperature measurement location within 15 minutes before a test is initiated and at least one hour after the masonry heater was closed in accordance with Section 5.8.2.3. Response Time - the amount of time required for a gas measurement system to respond and 
display 90% of a step change in the analyte gas concentration. 
Sampling System Bias - the difference between the gas concentrations displayed by an analyzer 
when a gas of known concentration is introduced at the inlet of the sampling probe and the gas 
concentration displayed when the gas of known concentration is introduced directly to the 
analyzer. 
Span - the upper limit of a gas concentration measurement range. (Typically 25% for CO 2 , O2 
and 5% for CO.) 
Test-Burn or Test Period - the time from when flue-gas temperatures rise above 25 ° F over the 
pretest flue-gas temperature after ignition of the test fuel to the time flue-gas oxygen 
concentrations have recovered to 95% but not more than 97% of the maximum flue-gas oxygen 
depression caused by the last fuel charge of the required three consecutively-burned test fuel charges and the consumption of at least 90% of the total mass of the three consecutively-burned 
test-fuel charges. 
Test Facility - the building enclosure in which the masonry heater is installed, operated, and 
sampled for emissions. 
Test-Fuel Charge - one of three test-fuel cribs burned during a test period. 
Test-Fuel Loading Factor - the ratio between test-fuel crib volume including inter-fuel-piece 
spacing, and the usable firebox volume. For this Standard, the test-fuel loading factor for masonry 
heaters is 0.30 (i.e., 30%). 
Usable Firebox Volume (F v) - the product of the useable hearth area and the average useable 
firebox height. Useable means the volumetric space within the fire chamber of a masonry heater 
into which fuel can be, or is intended to be, placed for firing. Usable firebox volume is calculated 
using the following dimensional definitions: 
Firebox Length - average length of at least nine equally-spaced lines running parallel to 
the greater of 1) the PH hd , or 2) the SH hd . 
Firebox Width or Depth - average length of at least nine equally spaced lines running 
perpendicular to the lines used for determining firebox length. 
Firebox Floor Versus Hearth Area - If a masonry heater has a larger floor area within the 
fire chamber than the area intended for fuel placement and burning, the useable hearth 
area shall be calculated as the sum of standard geometric areas or sub-areas of the area 
intended for fuel placement and burning. 
Firebox Height (Fb h) - the vertical dimension measured from the hearth of a masonry 
heater or the top of a fuel-elevating grate to the horizontal plane that intersects and is 
perpendicular to the top edge of the fuel loading door opening. 
Fuel-Elevating Grates - For masonry heaters with grates that elevate fuel charges above 
the hearth, the useable firebox area includes all geometric sub-areas within the total grate area or "foot print" circumscribed by the connection of all of the outer most grate projections. Useable hearth areas calculated using fuel-elevating grate dimensions shall 
be multiplied by a factor of 1.5 for determining fuel load charge volumes. The volume of 
test-fuel charges calculated using fuel-elevating grate areas shall not exceed the volume of test-fuel charges determined for the masonry heater hearth area. Vertical Flue-Gas Pathway - the total vertical duct centerline distance measured from the point 
where the vertical centerline of the flue-gas exit duct from the firebox intersects the horizontal plane of the firebox height (See definition for "Firebox Height" under “Usable Firebox Volume”) to 
the point where the centerline of the exhaust duct exit to the atmosphere intersects the horizontal 
plane at the total vertical extent (i.e., height) of the exhaust duct at the flue-gas exit to the atmosphere. For the purpose of these protocols, horizontal shall mean any amount of duct 
centerline traverse that is created by any angle that is either more or less than 90° or 270° from 
vertical. The length of a downward vertical flue-gas pathway is the total sum of all vertical flue-gas pathway distances (upward and downward flow direction) minus the total vertical distance measured from the horizontal plane of the firebox height to the total vertical extent of the flue-gas 
exit duct to the atmosphere. 
Zero Drift - the difference between the initial calibration response at the zero concentration level 
and the calibration response at the zero concentration level after a stated period of instrument 
operation during which no maintenance, repair, or adjustment took place. 
3.0 APPROVAL PROCEDURES 
3.1 Requirements for Approval. On or after June 1, 2006, a manufacturer or builder of a masonry 
heater who wishes to have a masonry heater model, model line, or masonry heater design 
designated as a Colorado APCD-approved masonry heater under Colorado Regulation Number 
4, shall submit to the Colorado APCD for its review the following information: 
3.1.1 Appliance Specifications. The masonry heater manufacturer's name, street address, 
masonry heater model, model line, or design identification, all masonry heater 
construction specifications, drawings of the masonry heater firebox and internal 
assembly, and all specifications for required chimney systems and emission control 
devices, and 
3.1.2 Test Report. A test report prepared in accordance with these Test Method Protocols 
showing that the arithmetically-averaged particulate emissions factor for all operating configurations tested on the candidate masonry heater does not exceed 6.0 grams of 
particulate emissions per kilogram (g/kg dry weight) of fuel burned; test-method-adjusted 
for equivalency to U.S. Environmental Protection Agency (EPA) Method-5H sampling 
system (Code of Federal Regulations Title 40, Part 60, Subpart AAA (2004)) results. 
3.2 Approval of Modifications Made to Tested and Approved Models. The Colorado APCD may grant 
approval for masonry heater internal assembly modifications that have been previously tested and Colorado APCD-approved upon submission of the following information by the applicant: 
3.2.1 Appliance Specifications. The previously-tested and APCD-approved masonry heater 
manufacturer's name, street address, model, model line, or design identification, all 
construction specifications, drawings of the masonry heater firebox and internal 
assembly, and all specifications required for chimney systems and emission control 
devices. 
3.2.2 Comparison to Previously-Tested and Approved Model. Documentation from a Colorado 
APCD-accredited laboratory that the candidate modified masonry heater is a masonry heater within the definition of Colorado APCD Regulation Number 4, has substantially the 
same internal assembly as a masonry heater already tested by a Colorado APCD-
accredited laboratory, and is substantially similar to a Colorado APCD-approved masonry heater model, model line, or design in combustion function, and probable emissions 
performance as required by these Test Method Protocols. A modified masonry heater 
model, model line, or design shall be deemed to have the same "internal assembly" and 
be "substantially similar" to a tested and Colorado APCD-approved masonry heater 
model, model line, or design in combustion function, and probable emissions performance as required by Colorado APCD Regulation Number 4, if the modified 
masonry heater model, model line, or design meets all of the following acceptance criteria when compared to a previously tested and Colorado APCD-approved masonry 
heater model, model line, or design: 
3.2.2.1 Critical Dimensions. Table 3.2.2.1.1 presents a list of “critical” masonry heater 
dimensions. Measurements of these critical dimensions from a previously tested 
and Colorado APCD-approved masonry heater shall be compared to the critical dimension measurements of a masonry heater being submitted to the Colorado 
APCD for a modification approval. To qualify for Colorado APCD approval of a 
modification to a previously tested and Colorado APCD-approved masonry 
heater, each critical dimension measurement from the masonry heater being submitted for approval shall not exceed the tested-to-non-tested percentage 
differences presented in Table 3.2.2.1.1. In addition, no single linear critical-
dimension measurement difference shall be more than 5 percentage points 
different from any of the other linear critical dimension measurement differences; 
no measured critical dimension area difference shall be more than 10 percentage points different from any of the other corresponding area measurement 
differences; and no critical dimension volume measurement difference shall be 
more than 15 percentage points different from any of the corresponding volume measurement differences. 
Table 3.2.2.1.1 Critical Masonry Heater Dimensions   
Critical Dimensions Allowed ± Differences 1 (%) 
Average firebox width or depth 5 
Average firebox length 5 
Hearth area 10 
Average grate width or depth 5 
Average grate length 5 
Grate area 10 
Avera ge firebox hei ght 5 
Firebox volume 15 
Downward "vertical" distance of the flue-gas pathway 5 
Horizontal distance of the flue-gas pathway 5 
Flue-gas exhaust cross-sectional area 10 
Note 1: Allowed difference between a previously tested and Colorado APCD-approved masonry heater 
and a masonry heater being submitted for a Colorado APCD modification approval. 
3.2.3 Construction Materials. Without specific Colorado APCD approval, materials used for 
fabricating or building all of the internal assembly components of a modified masonry heater shall be identical, in all respects, to the materials used to fabricate or build the 
Colorado APCD-approved masonry heater. 
3.2.4 Emissions Factor Margin. The emissions factor margin of the tested Colorado APCD-
approved masonry heater shall be greater than 50% of the Colorado APCD masonry 
heater emissions factor standard (note, the emissions factor margin is defined in Section 
2.0). 
3.2.5 Test Report. A copy of, or appropriate reference information from, the original test report 
for the already tested and already Colorado APCD-approved internal assembly system. 
3.2.6 Notarized Affidavit. A notarized affidavit of ownership shall be provided for the previously 
tested and Colorado APCD-approved masonry heater submitted as the basis of 
comparison in an application for Colorado APCD approval of a modified masonry heater model, model line or design. Alternatively, an owner of a tested and Colorado APCD-
approved masonry heater shall submit a notarized affidavit of ownership along with an 
additional notarized affidavit stating the owner's approval for allowing the use of his or her 
Colorado APCD-approved masonry heater as the basis of comparison in an application 
for Colorado APCD approval of a specified non-owned, modified masonry heater. 
3.3 Re-Testing. A masonry heater shall be re-tested in accordance with the specifications of this 
Standard if it is determined during inspection that a design change has been incorporated into the 
Colorado APCD-approved masonry heater’s internal assembly which may adversely affect its 
emissions factor. Any and all internal assembly design changes shall cause the subject masonry heater to be considered as "affecting its emissions factor” and shall be deemed a "modified" 
appliance. In order to qualify for continued Colorado APCD approval without re-testing, the 
previously Colorado APCD-approved and modified masonry heater shall comply with all of the 
dimensional, proportionality, and construction material comparison and emissions margin criteria 
contained in Section 3.2.2. 
3.4 Permanent Label, Temporary Label, and Owner's Manual. 
3.4.1 Labels and Owner's Manual. Permanent and temporary labels and an owner's manual 
shall be prepared and included with all Colorado APCD-approved "For Sale" masonry heaters as specified for wood heaters in Title 40 of the Code of Federal Regulations (CFR) Part 60, 60.536. Information that shall be presented on all labels includes: 
 manufacturer's or builder's name, address, and phone number; 
 masonry heater model, model line, or design number and/or name; 
 month and year of manufacture or construction, if site-built; 
 on all Colorado APCD-approved masonry heaters, the label shall state: "This 
appliance has been tested and has demonstrated compliance with Colorado APCD, 
Regulation Number 4 requirements; and 
 the name, city and state address, and the registered service mark (i.e., U.S. 
Patent and Trademark Office, Washington, DC) of the Colorado APCD-accredited 
laboratory that conducted the testing for Colorado APCD approval. 
3.4.2 Closed-Door Operation Label. A permanent label shall be secured in a location on or 
near the fuel-loading door handle(s) or fuel-loading opening so that it is readily and easily 
read by consumer users. This label shall state: "Except For Fuel Loading Operations, The 
Fuel-Loading Door(s) Of This Masonry Heater Must Remain Closed At All Times." 3.4.3 Fuel-Elevating Grate/Operation Label. If a masonry heater was not tested with and 
without a fuel-elevating grate, an additional permanent label shall be secured in a location on or near the fuel-loading-door handle(s) or fuel-loading opening so that it is 
readily and easily read by consumer users or, as an alternative, an addition to the 
“closed-door operation” label specified in Section 3.4.3 shall be made. This label or label addition shall state: "This Masonry Heater Is Not Colorado APCD-Approved for Operation 
With (or Without; use the appropriate term) A Hearth Fuel-Elevating Grate." 
3.4.4 Low Air-Supply Operations. For masonry heaters with air supply controls, or if a masonry 
heater cannot or is not intended to operate at its lowest air supply setting, a permanent 
instruction label shall be prominently affixed to the masonry heater air supply control 
mechanism. The label shall be affixed so that it is readily visible and readable to any person operating the control. This instruction label shall state: "This air supply control 
must be set to the “Normal” position during all firing periods." The 
builder’s/manufacturer’s owner’s manual shall define “Normal” as the air supply position 
that has been tested and shown to be the optimum position for obtaining the lowest 
emissions and highest thermal efficiency. 
3.5 Emissions Control Devices. 
3.5.1 Label Requirements. If a masonry heater is tested and Colorado APCD-approved with a 
non-integral emissions control device, the label shall state that "It is illegal to sell, install, or use this masonry heater in Colorado without (insert the model name and manufacturer 
of the specified emissions control device here) installed and operating." 
3.5.2 Lock Out Requirements. Additionally, masonry heater models approved by the Colorado 
APCD with non-integral emissions control devices shall have “lock out” master control 
systems to prevent masonry heater use without the emissions control device operating in 
a manner equivalent to its operation during the certification tests conducted for its Colorado APCD approval. 
3.5.3 Non-Tested Models. Qualifying emissions control devices may be approved by the 
Colorado APCD for use on various additional non-emissions-tested masonry heater 
models. To qualify for Colorado APCD approval for use on a non-emissions-tested 
masonry heater model, an emissions control device shall first be tested on a masonry heater in accordance with this standard and the resulting emissions factor shall be less 
than 1.0 g/kg. An emissions control device meeting this requirement may then be 
approved for use on non-emissions-tested masonry heaters that demonstrate, using the 
fueling and flue-gas measurement protocols of this standard, a burn-period maximum air-to-fuel ratio of less than the maximum air-to-fuel ratio measured during the qualifying 
Colorado-APCD-approval masonry heater test period(s) but not less than 9:1; and an 
average flue-gas flow rate less (ft3/min, m3/min) than the average flue-gas flow rate 
measured during the qualifying Colorado-APCD-approved masonry heater test periods. 
Air-to-fuel ratio (A/F) for this determination shall be calculated using Equation 3.5.3.1 as follows: 
 3.5.3.1 Alternate Air-to-Fuel Ratio. If the alternative CO 2 +CO flue-gas concentration 
recovery is used as the criteria for required fuel charging and test completion 
times instead of oxygen recovery, see Sections 5.8.8.1 and 5.8.12.1, A/F may be 
calculated using Equation 3.5.3.1.1 as follows: 
 
3.6 List of Colorado APCD-Approved Masonry Heaters. The Colorado APCD shall maintain a list of 
Colorado APCD-approved masonry heater models, model lines, and designs at its Denver, 
Colorado offices, and that list shall be available to the public. 
4.0 TEST LABORATORY ACCREDITATION 
A Colorado APCD-accredited testing laboratory shall conduct all of the testing, test reporting, and 
inspection requirements. 
4.1 Laboratory Accreditation Requirements. In order to qualify for Colorado APCD accreditation, the 
test laboratory shall be accredited: 
 by the U.S. Environmental Protection Agency (EPA) for testing wood-burning residential 
space heaters in accordance with 40 CFR Part 60, Subpart AAA (2015), Section 60.535, and 
 by the American National Standards Institute (ANSI) to the International Standards 
Organization (ISO) Standard ISO/IEC Guide 65 General Requirements for Bodies Operating 
Product Certification Systems ; and 
 by a nationally recognized accreditation body to ISO/IEC 17025, General Requirements 
for the Competence of Testing and Calibration Laboratories. The nationally recognized 
accrediting body shall operate under ISO Guide 58 (Calibration and Testing Laboratory 
Accreditation Systems - General Requirements for Operation and Recognition). 
5.0 TESTING 
5.1 Applicability and Principal. The methods and protocols described in this section are applicable to 
the Colorado APCD approval of wood-burning masonry heaters and the determination of 
particulate emissions factors. Emissions measurements for this Test Standard are performed on 
a masonry heater installed and operated in accordance with the following protocol components: 
Emissions are sampled from masonry heater flue gases using an emissions sampling system 
(ESS) described in Section 5.3.11; Flue gases are drawn through a stainless-steel sample probe, 
a heated sample line, a fiberglass filter, and a cooled sorbent resin for determining non-volatile as well as semi-volatile particulate emissions; Sampled combustion gases are analyzed for oxygen 
(O2), carbon dioxide (CO 2), and carbon monoxide (CO) concentrations which are subsequently 
used for calculating fuel loading time criteria, flue-gas flow rates, and emissions factors. 
5.1.1 Alternative Sampling and Measurement Systems. Upon approval by the Colorado APCD, 
qualified alternative emissions sampling methods may be used as equivalent methods to those prescribed. To qualify as equivalent, a candidate alternative method(s) shall be 
performed by a Colorado APCD-accredited laboratory in accordance with the U.S. EPA 
Method 301 Field Validation Procedure (Federal Register, December 12, 1992; Volume 
57, Number 250, page 11,998). In order to qualify for alternative sampling system approval, the results of the qualifying EPA Method 301 tests shall comply with the U.S. 
EPA Field Validation acceptance criteria. 
5.2 Test Configurations. All masonry heaters shall be tested in any and all of the configurations listed 
in Section 5.2.1 for which the manufacturer or builder seeks Colorado APCD approval. 
5.2.1 Minimum Required Masonry Heater Test Configurations. One, three-fuel-charge test-
period shall be conducted for whichever of the following operating configurations is 
applicable: 
 door(s) closed, with a fuel-elevating grate; and 
 door(s) closed, without a fuel-elevating grate. 
5.2.2 Test Configurations Not Required. No test-burn shall be required for any configuration the 
appliance design cannot or is not intended to accommodate. If a possible configuration is 
not tested, the reason(s) must be submitted with the test report and the permanent label, as specified in Section 3.4, must state that the masonry heater may not be used in that 
non-tested configuration by a consumer. 
5.2.3 Closed-Door(s) Testing. For all test configurations, the fuel loading door(s) shall be 
closed within 10 minutes after the addition of the first test-fuel piece of each test-fuel 
charge in a test-burn. During a test-burn period, the fuel loading door(s) shall not be re-
opened except during test-fuel reload and adjustment as provided for in Section 5.8.9. 
5.2.4 Additional Tests. The testing laboratory may conduct more than one test for each of the 
applicable configurations specified in Section 5.2.1. In the event more than one test is conducted for a specified configuration, the results from at least two-thirds of the tests for 
that configuration shall be used in calculating the arithmetic average emission factor for 
that configuration. The measurement data and results of all tests conducted shall be reported regardless of which values are used in calculating the average emission factor for that configuration. 
5.3 Test Apparatus. The following test equipment is required for the performance of the emissions 
sampling procedures contained in this Test Standard. 
5.3.1 Masonry Heater and Flue-Gas Temperature Sensors. Device(s) capable of measuring 
flue-gas temperature to within 1.0% of expected absolute temperature values. 
5.3.2 Test Facility Temperature Sensor. A device located centrally in a vertically oriented pipe 
shield 6 inches (150 mm) long and 2 inches (50 mm) in diameter that is open at both 
ends and capable of measuring air temperature to within 1.0% of expected absolute 
temperature values. 
5.3.3 Desiccator. A desiccator for maintaining all particulate sample residues at constant room 
temperature and the relative humidity levels required in 40 CFR Part 60 Appendix A, U.S. EPA Method 5. 
5.3.4 Soxhlet Extractors. Soxhlet extractors for extracting semi-volatile particulate emissions 
residues from the XAD-2 sorbent-resin. 
5.3.5 Scale. Electronic strain-gauge scale capable of accurately weighing 220-pound (100-kg) 
test-fuel charge(s) to within 0.1 pound (0.05 kg). 5.3.6 Analytical Balance. An analytical balance capable of weighing sample filters, and 
sorbent-resin and equipment-rinse particulate residues to the nearest 0.1 mg. 
5.3.7 Wood-Fuel Moisture Meter. Calibrated Delmhorst® or equivalent electrical resistance 
meter for measuring test-fuel moisture at a depth of 1 inch to within 1% moisture content 
(dry basis). 
5.3.8 Anemometer. Device capable of measuring air velocities of 20 feet/minute (0.10 
m/second), for measuring air velocities near the masonry heater being tested. 
5.3.9 Barometer. A barometer capable of measuring atmospheric pressure to within 0.02 
inches (0.50 mm) of mercury. 
5.3.10 Draft Gauge. Electro-manometer or inclined liquid manometer for the determination of 
flue/chimney draft (i.e., static pressure) readable to within 0.02 inches of water column 
(1.0 Pa). 
5.3.11 Emissions Sampling System (ESS). Figure 5.3.11.1 shows a schematic diagram of an 
ESS used for sampling wood-fired masonry heater emissions. The ESS shall consist of 
the following component specifications. 
5.3.11.1 Flue-Gas Sample Probe. A stainless-steel probe with 3/8 inch (10 mm) 
O.D. and at least long enough to reach the center of the flue/chimney at the flue-gas sampling and temperature measurement location as specified in Section 
5.7.3. The stainless-steel probe shall be fitted with a stainless-steel 3/8 inch (10 
mm) diameter leading edge but ton-hook nozzle to provide a 90° turn of the sampling probe into the direction from which the flue-gas stream flows. 
5.3.11.2 Sampling Line. If the sampling line length from the probe to the ESS filter 
inlet is less than 8 feet (2.4 m), 3/8 inch (10 mm) I.D. Teflon® tubing may be used. However, if the distance is greater than 8 feet (2.4 m) a heated 3/8 inch (10 
mm) I.D. Teflon® sampling line, not to exceed 18 feet (5.5 meters), shall be used 
to make the connection between the stai nless-steel sampling probe and the ESS. 
Non-heated 3/8 inch (10 mm) I.D. Teflon® tubing shall be used to make all of the 
other necessary ESS connections upstream from the XAD-2 cartridge as shown 
in Figure 5.3.11.1. 
5.3.11.3 Flue-Gas Sampling Process. Upon entering the ESS, the flue-gas 
sample stream shall travel through a heated U.S. EPA Method 5-type glass-fiber 
filter (40 CFR Part 60 Appendix A) for collection of particulate matter. The filter shall be followed by a cooled, in-line flow-through cartridge containing 20 to 25 grams of XAD-2 sorbent resin for collecting semi-volatile hydrocarbon 
compounds. Water vapor shall then be removed from the sampled flue-gases by 
a cooled condensate trap with a volume of no more than 100 ml. Sampled flue-gas oxygen concentrations shall be measured within the ESS flue-gas sampling system or by a separate flue-gas sampling system with an electrochemical (or 
paramagnetic) sensor cell meeting the performance specifications presented in 
Section 5.3.14. 
5.3.11.4 Sample Flow Control. The ESS sha ll use a critical orifice to maintain a 
nominal but constant flue-gas sampling rate in the range of 0.035 cubic feet (1.0 liter) per minute to 0.106 cubic feet (3.0 liters) per minute, less than or equal to 
10%. The critical orifice shall be calibrated through an operating temperature 
range of 50-200° F (10-95° C). The resulting calibration curve shall be used to correct the sampling rates taking place during each test period. 5.3.11.5 Flow Meter. Rotameter with flow-control valve in the 0 to 1.0 cubic-foot 
per hour (0 to 500 ml per minute) range. 
5.3.11.6 Condenser/Dryer. Low-volume (i.e., less than 100 ml total volume) 
Midget glass impinger(s). 
 
5.3.11.7 Filter. An in-line filter to remove solids and condensable materials from 
the sampled flue-gas stream. The filter can be fiberglass or glass wool. 
Disposable filter cartridges may also be used. 
5.3.12 Linear-Measure Device. A standard-verified meter stick or tape measure capable of 
measuring increments of 0.1 inch (2 mm). 
5.3.13 Vacuum Gages. Vacuum gage with a range of 0 to 30 inches of mercury. 
5.3.14 Gas Analyzers. Gas analyzers with capabilities for measuring carbon dioxide (CO 2) in 
the range of 0.0 to 20.0%, carbon monoxide (CO) in the range of 0.00 to 5.00%, and 
oxygen (O 2) in the range of 0.0 to 25.0% in flue-gas samples shall be used for 
conducting the gas analysis requirements of these Test Method Protocols. Each gas 
analyzer shall meet the following measurement system performance specifications: 
5.3.14.1 Analyzer Calibration Error. The error shall be ≤ 2 percent of the span 
value for the high-range calibration gas used. 
5.3.14.2 Sampling System Bias. The bias shall be ≤ 3 percent of the span value 
for the high-range calibration gas used. 5.3.14.3 Zero Drift. The drift shall be ≤ 2 percent of the high-range span value for 
the high-range calibration gas used. 
5.3.14.4 Calibration Drift. The drift shall be ≤ 2 percent of the high-range span 
value for the high-range calibration gas used. 
5.3.14.5 Analytical Interference. The interference of CO measurements caused by 
the presence of CO 2 in flue-gases shall be determined by the sampling of high-
range CO 2 calibration gas through the carbon monoxide analyzer system. A 
calibration gas in the range of 10% to 12% CO 2 and 0.00% CO by volume shall 
not cause the CO analyzer to indicate a measurement of more than 0.20% CO. 
5.3.14.6 CO 2 Gas Analyzer Accuracy Limitation. If the average test-period flue-
gas CO 2 plus CO is not greater than 3.0%, the CO 2 analyzer shall have a 
resolution of at least 100 parts per million (0.01 %) 
5.4 Sampling Supplies and Reagents. 
5.4.1 Calibration Gases. Calibration gases for each flue-gas constituent to be measured shall 
have concentrations at each of the nominal ranges indicated in Table 5.4.1.1. Mixtures or 
combinations of calibration gases may be used in place of separate cylinders for each calibration constituent. 
 
Table 5.4.1.1 Nominal Calibration Gas Concentrations  1 
Range: Oxygen Carbon Dioxide Carbon Monoxide  
High 19 - 21% 17 - 21% 1.0 - 2.5% 
Mid 8 - 12% 8 - 12% 0.60 - 1.0% 
Low 0 - 4% 0 - 4% 0 - 0.50% 
Note 1: All calibration gas mixtures shall be certified by the calibration gas supplier or a laboratory 
meeting the requirements of Section 4.1 using the reference methods contained in Title 40 Code of 
Federal Regulations, Part 60, Appendix A: Methods 3 and 10. 
5.4.2 Dichloromethane (Methylene Chloride). Reagent grade or better. (Report blanks for each 
supply batch.) 
5.4.3 Methanol. Reagent Grade or better. (Report blanks for each supply batch.) 
5.4.4 Sample Filter. Type A/E glass-fiber filters rated at 99.9% removal of particulate matter 0.3 
microns aerodynamic diameter: 102 mm diameter. 
5.4.5 XAD-2 Sorbent Resin. The XAD-2 sorbent resin shall be Amberlite® or equivalent and 
shall not produce blank residues of 2.0 mg per 25 grams of XAD-2 when extracted in 
dichloromethane for 24 hours. 
5.5 Test Fuel. 
5.5.1 Species. Test fuel shall be Douglas fir. 5.5.2 Fuel Piece Cross-Sectional Dimensions. For average firebox heights of more than 12.0 
inches (305 mm), test fuel pieces shall consist of air-dried 1.5- by 3.5-inch (38- by 89-mm) and 3.5- by 3.5-inch (89- by 89-mm) actual-dimension lumber. 
5.5.2.1 Small Fireboxes. For average firebox heights equal to or less than 12.0 inches 
(305 mm) (e.g., bake ovens), the height of each fuel piece and all vertically 
positioned fuel crib spacers shall be reduced proportionally to the amount the 
firebox height is less than 12.0 inches (305 mm). Adjusted fuel piece and spacer height shall be calculated using Equation 5.5.2.1.1 as follows: 
FPah = FP sh x AF h / 12 inches (305 mm) Equation 5.5.2.1.1 
Where: FP ah = Adjusted fuel piece height 
FPsh = Standard fuel piece height: 3.5 inches (89 mm) 
AFh = Actual firebox height 
FPah shall be used in the equations in Section 5.5.7.3 for calculating the number 
of fuel piece layers in each fuel crib. 
5.5.3 Fuel Moisture Content. Fuel moisture content is the average of 1-inch deep moisture 
measurements made at three locations on each fuel piece; one each no closer than 2.0 inches (51 mm) from each end and one near the middle of the fuel piece length. The 
average fuel moisture of each fuel piece shall be in the range of 19 to 25% dry basis (16 
to 20% wet basis). 
Note: Most wood moisture meters measure in dry-basis percent. Verify the moisture 
meter specifications to confirm its moisture basis measurement type. 
5.5.4 Test-Fuel Cribs. Test fuel loads shall be constructed into multi-layered structures referred 
to herein as “fuel cribs” or “fuel charges”. The overall length, width, and height of fuel 
cribs are equally proportional to the average length, width, and height of the firebox being tested. Three separate fuel cribs shall be prepared for each test period. The first layer (i.e., the bottom layer) of the first fuel crib shall be made up of 1.5- by 3.5-inch (38- by 89-
mm) fuel pieces. The second and higher layers of the first fuel crib and the entire second 
and the third fuel cribs are made only of 3.5- by 3.5-inch (89- by 89-mm) fuel pieces. See Figures 5.5.4.1 and 5.5.4.2. 
5.5.4.1 Spacers. To provide equal spacing between all fuel pieces in a fuel crib, wood 
spacers with cross-sectional dimensions of 0.625- by 1.5-inch (16- by 38 mm) 
shall be placed laterally-centered between and on all fuel-piece sides facing 
other fuel-piece sides. No spacers are to be placed on the outward-facing fuel-
crib sides. See Figure 5.5.4.1.1  
  
5.5.5 Fuel Crib Dimensional Specifications. This section describes the procedure by which fuel 
crib dimensional specifications are determined for hearth perimeters delineated by at least three straight-line walls/sides around the hearth and hearth perimeters having at 
least one horizontal line of symmetry across the hearth. 
5.5.5.1 Fuel Crib Shape. All fuel cribs built to the specifications of this section will have 
rectilinear plan and length views. 
5.5.5.2 Primary and Secondary Horizontal Hearth Dimension Designation (PH hd and 
SHhd). The manufacturer or builder shall designate either the line of symmetry or 
the longest line drawn perpendicular to the line of symmetry as the PH hd along 
which the length of the fuel crib shall be oriented for burning. The longest line 
perpendicular to the PH hd is designated as the Secondary Horizontal Hearth 
Dimension (SH hd). 
5.5.5.2.1 Line of Symmetry. A line of symmetry is obtained by drawing a 
straight line across a plan-view drawing of the hearth area, or, if present, 
the fuel elevating grate area so that the line bisects the hearth or fuel-
elevating grate area into mirror images. For hearth or fuel-elevating grate areas that have more than one line of symmetry, only one shall be 
chosen as the PH hd . This standard makes no preference or 
specification of which one is chosen. 
5.5.5.2.2 Average PH hd . Determine the average PH hd from the lengths 
of at least nine lines equally spaced and parallel to the PH hd along the 
whole length of the SH hd . 
5.5.5.2.3 Average SH hd . Determine the average SH hd from the lengths 
of at least nine lines equally spaced and parallel to the SH hd along the 
whole length of the PH hd . 
5.5.5.3 Average Firebox Height (F bh). If there are inwardly slanted or curved firebox 
walls or other downward physical projections, an average firebox height shall be 
determined using vertical dimensions measured from the hearth or top of a fuel-elevating grate to the horizontal plane that intersects and is perpendicular to the 
top of the fuel loading door opening or any lower projection directly above the centers of at least nine closely-equal and square hearth sub-areas, none of 
which exceeds 16 square inches (100 square centimeters). 
5.5.5.4 Total Useable Hearth Area (H ua). Determine the total usable hearth area (H ua) 
or, if present, the total horizontal plan area of the fuel elevating grate. 
5.5.5.5 Useable Firebox Volume (F v). Calculate useable firebox volume by multiplying 
the average F bh (or, if applicable, the F bha) by H ua. 
5.5.5.6 Fuel-Crib Volume (F cv). Calculate the fuel-crib volume (F cv) as 30.0% of the F v. 
5.5.5.6.1 Fuel-Elevating Grate. Fuel-crib volume calculated from a fuel-
elevating-grate-based H ua (see Fuel-Elevating Grate under the Firebox 
Volume definition in Section 2.0) shall not be greater than the fuel-crib 
volume calculated using a H ua derived from the whole useable hearth 
area. 
5.5.5.7 Fuel-Crib Dimension Sizing Factor (FC dsf). Determine the fuel-crib-
dimension/firebox-dimension sizing factor as the cube root of the fuel-crib-
volume/firebox-volume loading factor. 
 
5.5.5.8 Fuel-Crib Length (FC l) and Target Fuel-Crib Width (FC tw) and Height (FC th). 
Determine FC l, FCtw, and FC th using the following equations: 
FCl = PH hd x FC dsf Equation 5.5.5.8.1 
FCtw = SH hd x FC dsf Equation 5.5.5.8.2 
FCth = FB h x FC dsf Equation 5.5.5.8.3 
5.5.6 Fuel Piece Spacing. The 0.625 inch (16 mm) vertical and horizontal spacing between 
parallel fuel pieces shall be made by nailing, with 18 gage by 1¼ inch (32 mm) finishing brads, 0.625- by 1.5- by 2.0-inch (16- by 38- by 51-mm) spacers positioned so their 1.5 inch (38 mm) longitudinal side centerline is “X” inches from and parallel to the 3.5 inch 
(89 mm) end edge of the fuel piece to which it is being attached: Where: X = 0.15 x F pl . 
These fuel-piece spacers are further positioned so the latitudinal centerline of the 1.5- by 
2.0-inch (38- by 51-mm) side of the spacer is perpendicular to the longitudinal spacer centerline and 1.75 inches (45 mm) from the longitudinal edge of the fuel-piece side to 
which it is being attached. To maintain 0.625 inch (16 mm) spacing between all fuel 
pieces, spacers should only be attached on alternating facing sides of each fuel piece. No spacers are to be attached to fuel-piece faces located on the outer-most faces of the fuel crib. Maximum spacing between all fuel pieces shall not exceed 0.625 inches (16 
mm). 
5.5.7 First Fuel-Crib Structure. 5.5.7.1 Number of Fuel Pieces in the Bottom (First) Layer (n1 1). The number of 
bottom/first layer pieces in the first fuel crib is the closest whole number result 
from Equation 5.5.7.1.1 as follows: 
n1 1 = (FC tw + 0.625 inches) / 2.125 inches Equation 5.5.7.1.1 (in/lb) 
n1 1 = (FC tw + 1.59 cm) / 5.40 cm Equation 5.5.7.1.2 (SI) 
Where: n1 1 = Number of fuel pieces in the first layer of the first fuel crib 
0.625 inches (1.59 cm) = Place holder for last spacer in each layer 
Note: When the result is X.50, round up if the preceding integer, 
x, is even and down if the integer, x, is odd. 
5.5.7.2 Number of Fuel Pieces in Additional Layers (n1 i). The number of 3.5- x 3.5-inch 
(89- x 89-mm) fuel pieces in each of the second, third, and higher layers (n1 i) of 
the first fuel crib and all layers of additional cribs, is the closest whole number 
result from the equation as follows: 
n1i = (FC tw + 0.625 + 0.69) / 4.125 inches Equation 5.5.7.2.1 (in/lb) 
n1i = (FC tw + 1.59 + 1.74) / 10.48 cm Equation 5.5.7.2.2 (SI) 
Where: n1 i = Number of fuel pieces in the ith layer when “i” is greater than 1 
0.625 inches (1.59 cm) = Place holder for last spacer in each layer 
0.69 inches (1.74 cm) = Factor for forcing an additional fuel piece in the 
event a partial piece of less than 0.333 is calculated. 
Note: When the result is X.50, round up if the preceding integer, 
x, is even and down if the integer, x, is odd. 
5.5.7.3 Number of Fuel Crib Layers (n fcl). The number of fuel-crib layers for each and all 
fuel cribs shall be the closest whole number result from the equation as follows: 
nfcl = (FC th + 0.625 + 0.69) / (FP h + 0.625) Equation 5.5.7.3.1 (in/lb) 
nfcl = (FC th + 1.59 + 1.74) / (FP h + 1.59) Equation 5.5.7.3.2 (SI) 
Where: n1 fcl = Number of fuel crib layers 
FPh = FP sh or FP ah (see Section 5.5.2) 
0.625 inches (1.59 cm) = Place holder for last spacer in each layer 
0.69 inches (1.74 cm) = Factor for forcing an additional fuel crib layer in 
the event a partial layer of less than 0.333 is calculated. 
Note: When the result is X.50, round up if the preceding integer, 
x, is even and down if the integer, x, is odd. 5.5.8 Second and Third Fuel-Crib Loads. Except as specified in Section 5.5.2.1, the second 
and third fuel-crib loads shall consist entirely of 3.5- by 3.5-inch (89- by 89-mm) fuel pieces nailed and fastened parallel to each other with 0.625 inch (19 mm) spacing 
between them. The number of pieces in each second and third fuel crib layer shall be 
equal to the number of pieces in the second and higher layers of the first fuel-crib load and the number of layers in each second and third fuel-crib load shall be equal to the 
number of layers in the first fuel crib load. 
5.5.9 Test-Fuel Crib Construction. All fuel pieces with attached spacers shall be positioned in 
place to form a rectilinear-shaped fuel crib. All the fuel pieces of the whole fuel crib are 
then secured in position by wrapping and twist-tying 12 gage bailing wire around each 
end of the crib’s longitudinal axis. If a fully constructed and bailing-wire-secured fuel crib cannot be safely loaded into the firebox or cannot fit through the test appliance’s fuel-
loading door, then whole fuel-crib layers may be loaded separately starting with the 
lowest layer and placing subsequently higher layers on top of each other without inter-
connecting bailing wire. Only in cases where whole fuel crib layers cannot be placed in 
the firebox safely or cannot fit through the test appliance’s fuel loading door can fuel crib layers be separated into smaller groups of fuel pieces or individual fuel pieces for loading. 
In any case, the fuel piece spacing and fuel crib layer and stacking configurations 
prescribed in this section shall be maintained. 
5.5.10 Fuel-Crib Alignment For Testing. Kindling loads and test-fuel-cribs shall be aligned for 
fuel charging and re-charging so that the lengths of the fuel pieces are parallel to the 
designated PH hd. 
5.5.11 Fuel Crib Weight. Within 30 minutes before testing is initiated, each fuel crib with all their 
fuel pieces and spacers shall be weighed to the nearest 0.1 lb (45 g) and recorded. 
5.5.12 Kindling. 
5.5.12.1 Kindling Preparation. For each test, a kindling bed or kindling stack shall 
be prepared for initiating test fire burning periods. Kindling fuel shall consist of 0.75- by 0.75-inch (19- by 19-mm), 0.75- by 1.5-inch (19- by 38-mm), and 1.5- by 
1.5-inch (38- by 38-mm) dimensioned lumber. Kindling fuel species shall be 
Douglas fir with a moisture content of not more than 15% dry basis. The kindling-fuel load weight is not part of the initial fuel-crib load weight but is in addition to it and is used in calculating total fuel used during a test period. For fireboxes with no fuel-elevating grate, the kindling bed shall consist of four layers of the 
specified kindling fuel pieces constructed or positioned as follows. See Figure 
5.5.12.1.1. 
5.5.12.1.1 First Layer. The first (bottom) kindling layer shall consist of two 
equal-length pieces of the 0.75- by 1.5-inch (19- by 38-mm) lumber cut to the length dimension of the fuel crib. These two pieces are placed on 
their 0.75 inch (19 mm) edge on the hearth parallel to the PH hd. 
5.5.12.1.2 Second Layer. The second kindling layer shall consist of two 
equal-length pieces of the 0.75 - by 1.5-inch (19- by 38-mm) lumber cut 
to the fuel crib width dimension, placed on their 0.75 inch (19 mm) edge on top of the two-piece first layer and perpendicular to the first layer 
pieces. The ends of the second layer, (i.e., top) two pieces shall be 
positioned so that the ends of all first- and second-layer pieces meet to 
form right-angled corners. All first and second layer pieces shall be 
fastened together at the corners by nailing a 3 inch (73 mm) length of 0.75- by 0.75-inch (19- by 19-mm) kindling fuel into the inside of each 
corner using 18 gage by 1.25 inch (32 mm) brads. 
 
5.5.12.1.3 Newspaper. Crumple one full, double-tabloid-width 
(approximately 650 square inches (4200 cm2)) of newspaper for every 50 square inches (323 cm2) of horizontal fuel crib area and place them 
with even spacing and without excessive compression, within the space 
created by the first two kindling bed layers. 
5.5.12.1.4 Third Layer. The third kindling layer shall consist of 0.75- by 
0.75-inch (19- by 19-mm) lumber cut to equal lengths that are cut to the 
fuel crib length dimension. Enough of these pieces are prepared so that they can be placed at 1.5 inch (38 mm) center-to-center intervals all the 
way across the top of, and perpendicular to the second layer pieces. 
5.5.12.1.5 Fourth Layer. The fourth kindling layer shall consist of the 1.5- by 
1.5-inch (38- by 38-mm) lumber cut to equal lengths that are cut to the fuel crib width dimension. Enough of these pieces are prepared so that 
they can be placed at 2.5 inch (64 mm) center-to-center intervals all the 
way across the top of, and perpendicular to the third-layer pieces. 
5.5.12.2 Small Firebox. If the average firebox height is less than 12 inches (305 
mm), the height of each kindling piece shall be reduced in proportion to the 
amount the firebox height is less than 12 inches (305 mm). Kindling piece height shall be adjusted using the Equation 5.5.12.2.1 as follows: 
KPah = KP sh x AF h / 12 inches (305 mm) Equation 5.5.12.2.1 Where: KP ah = Adjusted kindling piece height 
KPsh = Standard kindling piece height: 0.75 inches or 1.5 inches (19 mm 
or 38 mm) 
AFh = Actual firebox height 
5.5.12.3 Firebox with Fuel-Elevating Grate. For fireboxes with a fuel-elevating 
grate, one layer of 1.5- by 1.5-inch (38- by 38-mm) kindling fuel shall be added to 
the base 4-layer kindling bed for every 2.0 inches (51 mm) of fuel elevation 
above the hearth. Added layers shall be placed perpendicular to the length of the pieces making up the layer immediately below. In the event of a partial 2.0 inch 
(50 mm) fuel-elevating grate-height increment, a partial kindling layer shall be 
prepared. The partial layer shall have a kindling fuel volume directly proportional to the partial height increment of the fuel-elevating grate. For example, a fuel-elevating grate height above the hearth of 3.0 inches (76 mm) shall have: 3 / 2 (76 mm / 50 mm) = 1.5 additional layers of 1.5- by 1.5-inch (38- by 38-mm) 
kindling. The 0.5 partial layer shall have 0.5 of the volume of a whole 1.5- by 1.5-
inch (38- by 38-mm) fuel-piece layer. Partial kindling-layer pieces shall be cut to the same length as full-layer pieces and placed at equal intervals onto the previous layer. 
5.5.12.4 Kindling Weight. Within 30 minutes before test initiation, the total weight 
of all kindling pieces shall be measured to within 0.1 lb (45 g) and recorded. 
5.6 Calibration and Audit Requirements. 
5.6.1 Scale. Within three hours before the initiation of a test, the scale used for weighing test-
fuel charges shall be audited by weighing at least one calibration weight (Class F) that is 
in the range of 20 to 80% of the expected test-fuel charge weight. If the scale cannot 
reproduce the value of the calibration weight within 0.1 pound (0.05 kg), re-calibrate the scale before use with at least three calibration weights spanning the operational range of the scale. 
5.6.2 Temperature Measurement Devices. Calibrate the temperature measurement devices 
before the first test period and semiannually thereafter. 
5.6.3 Fuel Moisture Meter. Calibrate the fuel moisture meter in accordance with the 
manufacturer's instructions within one hour before measuring fuel moisture. 
5.6.4 Anemometer. Calibrate the anemometer in accordance with the manufacturer's 
instructions before the first test period and semiannually thereafter. 
5.6.5 Barometer. Calibrate the barometer against a mercury barometer before the first test 
period and semiannually thereafter. 
5.6.6 Draft Gauge. Calibrate the draft gauge in accordance with the manufacturer's instructions 
before the first test period and semiannually thereafter. 
Note: An inclined liquid manometer does not require calibration but must be checked for 
level (zero tilt) before each test period. 
5.6.7 Sample Gas Flow Meters. Sample gas flow meters shall be calibrated once before the 
first test period and semiannually thereafter or once after every ten tests whichever 
occurs first. 5.6.8 Sample Flow Rates and System Response Times. ESS flue-gas sample and any other 
alternative flue-gas sampling system flow rate shall be set in accordance with Section 5.6.8.1 within two hours before sampling system response time is measured. The 
determination of response time for the ESS or an alternative gas sampling system shall 
be conducted before the first test period initiation and semiannually thereafter or at any time sampling system flow control components are changed. 
5.6.8.1 Response Time Measurement. The response time for all flue-gas sampling 
systems shall be determined by the measurement of a step change in analyte 
gas concentration. First, supply a low-range analyte calibration gas (see Table 
5.4.1.1) into the sample probe inlet end until the certified calibration gas 
concentration is measured. After the low range analyte is measured, switch the probe to a high-range calibration gas and immediately start timing the system 
response time. Response time shall be measured starting at the time the sample 
probe is switched from the low-range analyte calibration gas to high-range 
calibration gas and ending at the time the respective analyte analyzer reading is 
90% of the difference in calibration gas concentrations utilized. 
5.6.8.2 Response Time Limitation. Response time for all gas-sampling analyzers shall 
not exceed 1.0 minute for the ESS flue-gas sub-sample system. 
5.7 Test Preparations. 
5.7.1 Masonry Heater Installation. The masonry heater being tested must be constructed, if 
site-built, or, if manufactured, installed in accordance with the designer’s/manufacturers 
written instructions. These shall be the same instructions provided by the manufacturer or 
builder to the homeowner/consumer. The chimney shall have a total vertical height above 
the hearth of not less than 15 feet (4.6 m) nor more than 18 feet (5.5 m). The masonry 
heater chimney exit to the atmosphere must be freely communicating with the masonry heater combustion makeup-air source. There shall be no artificial atmospheric pressure 
differential imposed between the chimney exit to the atmosphere and the masonry heater 
make-up air inlet. 
5.7.2 Masonry Heater Description. Record masonry heater and, if equipped, catalyst and/or 
add-on emissions control device descriptions. The recorded masonry heater description shall include photographs showing all externally observable features and drawings 
showing all internal and external dimensions needed for fabrication and/or construction. 
The drawings must be verified as representing the tested masonry heater and signed by 
an authorized representative of the Colorado APCD-accredited testing laboratory. 
5.7.3 Primary Flue-Gas Sampling and Temperature Measurement Location. The Primary ESS 
sampling probe shall draw its flue-gas sample stream from near the center of the flue at a location which is at least 6.0 effective flue/chimney duct diameters (as calculated using Equation 2.1) upstream from the flue exit to the atmosphere or 8 feet (2.44 m) above the 
hearth whichever is the least flue-gas exhaust-duct center-line distance from the firebox 
hearth. The flue-gas temperature probe shall also be positioned near the center of the flue/chimney duct at the flue-gas sampling location but shall not interfere in any way with 
the ESS sample probe inlet. 
5.7.3.1 Add-On Emission Control Equipment. If a masonry heater is equipped with an 
emissions control device located in the flue/chimney duct, downstream from the 
masonry heater firebox, the primary ESS flue-gas sampling and temperature measurement locations shall be re-positioned immediately downstream from the emissions control device but not less than 6.0 effective flue diameters upstream 
from the flue exit to the atmosphere. An ESS flue-gas sampling and temperature 
measurement location positioned immediately downstream from an emissions control device shall meet the flue-gas stratification requirements of Section 
5.7.5.2. 
5.7.3.1.1 Fueled Emissions Control Devices. If a masonry heater is 
equipped with an emissions control device that requires additional 
energy provided by the combustion of any fuel input, a real-time flue-gas 
oxygen analyzer shall be located at the original primary ESS flue-gas 
sampling and temperature measurement location specified in Section 5.7.3. Test period real-time oxygen concentrations indicated by this 
analyzer, upstream from the emissions control device, shall be used for 
determining fuel recharge and test completion times and test period air-
to-fuel ratios. 
5.7.4 Test Facility Ambient Temperature Probe. Locate the test-facility ambient temperature 
probe on the horizontal plane that includes the primary air intake opening for the masonry heater. Locate the temperature monitor probe at a distance of 3 to 6 feet (1 to 2 meters) from the front of the masonry heater and in a 90° sector defined by lines drawn at ± 45 ° 
from a perpendicular line to centerline of the masonry heater face. 
5.7.5 Heat-Aging, Curing, and Durability Confirmation. A masonry heater of any type shall be 
operated at under “normal” conditions before certification testing begins. Operate the 
masonry heater using the fuel described in Section 5.5 for at least ten hours. Record and report the hours of operation and weight of all fuel burned during the aging, curing and 
durability confirmation period. 
5.7.5.1 Catalyst and/or Add-On Emissions Control Device-Equipped Masonry Heaters. 
Operate a catalyst and/or add-on emissions control-equipped masonry heater 
using fuel described in Section 5.5 for at least 50 hours prior to conducting a test. 
Record and report hourly catalyst temperatures and add-on emissions control equipment operating parameters during the hours of operation and the weight of 
all fuel burned during the heat-aging, curing, and durability confirmation period. 
5.7.5.2 Flue-Gas Stratification Check. During the masonry heater heat-aging and curing 
period specified in Section 5.7.5, use the oxygen analyzer and sampling system 
specified in Section 5.3.14 to determine whether flue gases become stratified in the flue/chimney cross-section at the primary emissions sampling and 
temperature measurement location specified in Section 5.7.3. 
5.7.5.2.1 Stratification of Flue-Gas Oxygen Concentrations. The 
stratification of flue-gas oxygen concentrations shall be determined by 
first sampling at the center of the flue/chimney at the flue-gas sampling 
and temperature measurement location for at least 15 seconds but not more than one minute and then moving the sampling probe to within 1 inch (25.4 mm) of the flue chimney wall for at least 15 seconds but not 
more than one minute. This procedure is to be repeated on at least two 
horizontal and perpendicular traverses of the flue/chimney cross-section. Flue-gas oxygen concentration differences of more than 15% of the 
highest oxygen concentration measured at any of the other three cross-
section sample points shall be considered stratified. 
5.7.5.2.2 Stratification Remedy. The presence of a stratified flue-gas flow 
regime at the emissions sampling location shall be remedied by either changing the flue/chimney duct design or changing the flue-gas sampling and temperature measurement probes to ones that equally and 
simultaneously sample the flue-gases and temperatures in the center of 
at least four separate and equal areas of the flue/chimney cross-section. 5.7.6 Leak Check. A leak check of the ESS and any other alternative flue-gas sampling system 
shall be performed within two hours before each test period initiation. Leak checks shall be performed as follows. 
5.7.6.1 Leak-Check Procedure. Seal the sample inlet probe-nozzles for each sampling 
system or train. Use the sample pump controls to create a vacuum greater than 
either twice the maximum vacuum encountered during test period sampling, or 5 
inches (125 mm) of mercury, whichever is greater. Record the resulting sample flow rate indicated by the instrument flow meter when the required vacuum is 
achieved, corrected for system pressure, if applicable. 
5.7.6.2 Leak Check Acceptance Criteria. Unless the leakage rate under the required 
vacuum is less than 2% of the average sample flow rate, analysis results shall be 
invalid. 
5.7.7 ESS Pre-Test Set-Up. 
5.7.7.1 XAD-2 Cartridge. Within 72 hours before each test period, the XAD-2 cartridge 
shall be processed as described in Section 5.8.14.2 for the determination of an 
XAD-2 resin blank. No XAD-2 resin blank that exceeds 2 mg per 25 gram batch 
of XAD-2 resin shall be used for any test. 
5.7.7.2 ESS Flow Rate. Within 72 hours before each test-burn, the ESS flow rate shall 
be confirmed to within 0.0007 cubic feet (0.02 liters) per minute using the temperature-corrected critical orifice flow calibration curve and a standardized 
volumetric bubble-type flow meter. 
5.8 Masonry Heater Operation and Testing Protocols. 
5.8.1 Masonry Heater Cooling Period. No fuel shall be burned in the test masonry heater and 
no other means for heating the masonry heater shall be used within the 12-hour period 
preceding test period initiation. 
5.8.2 Pre-Test Procedures. 
5.8.2.1 Room-Air Velocity. Using an anemometer, measure and record the room-air 
velocity within 2 feet (0.6 meters) of the test masonry heater air supply duct 
intake or fuel loading door within one hour before test initiation. Air velocity at the 
specified locations shall be less than 200 feet/minute (61 m/minute). During a test period, no external means shall be used to affect air velocities within 2 feet 
(0.6 meters) of the masonry heater being tested. 
5.8.2.2 Barometric Pressure. Measure and record the barometric pressure within one 
hour before test period initiation. 
5.8.2.3 Flue-Gas Temperature Determination. At least one hour before initiating a test 
period (i.e., ignition of a fire in the masonry heater), close all air supply controls 
and the masonry heater door(s). After one hour of masonry heater air-supply and 
open-face-area closure and within 5.0 minutes before opening the door(s) or the 
other means for closing the open face area of the masonry heater to initiate test-fire ignition, measure and record the pre-test flue-gas temperature at the flue-gas 
sampling and temperature measurement location or at the upstream temperature 
measurement location of an emission control device, as provided in Section 5.7.3. 5.8.3 Test-Burn Ignition. The test burn may be started only with a match (i.e., no charcoal-
lighter torches or other devices), with or without paper, and/or with or without kindling. Completion of test-fuel charging and any manufacturer-/builder-prescribed start-up 
procedures shall be within 10 minutes after test initiation as described in Section 5.8.4. 
Note: Prior to fuel charge ignition in a masonry heater, it may be necessary to first 
establish an operational flue draft so that combustion gases exit properly through the 
convoluted venting path and out the chimney exit. Otherwise, initial firebox combustion gases might vent out the fuel-loading door or the fire might extinguish. Establish sufficient 
operating draft by first heating the venting path by burning paper and/or kindling, so that 
flue draft is at least 0.02" H2O measured at the 8-foot (2.44 meter) sampling level. Test 
measurements and sampling shall be initiated within 15 seconds of when flue-gas temperatures reach 25° F above pre-test flue-gas temperature as specified in Section 
5.8.2.3. The weight of paper and/or kindling used to initiate a draft for nominal masonry 
heater operation are not considered part of the fuel load charges and are not included in 
total fuel weight determinations. 
5.8.4 Test Period Initiation. Flue-gas sampling is initiated after the kindling and fuel have been 
ignited and within 15 seconds of when flue-gas temperatures at the center of the flue/chimney at the flue-gas sampling and temperature measurement location, or the 
upstream flue-gas sampling and temperature measurement location of an emissions 
control device as provided in Section 5.7.3, reaches 25° F (14° C) greater than the pre-test flue-gas temperature as measured in Section 5.8.2.3. 
5.8.5 Test-Time Sampling, Parameter Measurement, and Data Recording Requirements. Once 
all test sampling and temperature measurements have begun at test initiation in accordance with Section 5.8.4 (i.e., zero time), all test sampling, parameter 
measurement, and data recording requirements shall be conducted at each 5-minute 
interval and shall continue without interruption until the test is terminated in accordance with Section 5.8.12. Test-time sampling and temperature measurement parameters shall 
include: 
ESS Oxygen (O 2) (alternatively, real-time CO 2 +CO may be measured instead of O 2 ; 
see Sections 5.8.8.1 and 5.8.12.1). 
Temperatures: 
Flue-Gas 
Heated Sample Line (if used) Heated ESS Filter Cooled XAD-2 Cartridge ESS Moisture Condensate Trap ESS Critical Orifice 
All Flue-Gas Sample Train/System Sampling Rates 
Vacuum Across ESS Critical Orifice Draft Pressure at the Primary Sampling and Temperature Measurement Location 5.8.6 ESS Component Temperatures. During all test periods, the temperature of the following 
ESS components shall be controlled to the following specifications: 
 The heated sample line shall be maintained in a temperature range from 200 to 
250° F (95 to 121° C) during all sampling periods, 
 The glass-fiber filter and its holder shall be maintained in a temperature range 
from 200 to 250° F (95 to 121° C) during all sampling periods, and 
 The XAD-2 cartridge and the moisture condensate trap shall be maintained in a 
temperature range from 35 to 40° F (1.7 and 4.4° C) during all sampling periods. 
5.8.7 Test Facility Ambient Temperatures. Test facility ambient temperatures shall be 
maintained between 65 and 100° F (18 and 38° C) during all test periods. 
5.8.8 Test Fuel Additions. Test-fuel crib charges for a test-burn period shall be placed and 
burned in the fire chamber only after flue-gas oxygen concentrations have recovered (i.e., 
increased) to at least 70% but not more than 80% of the maximum flue-gas oxygen 
depression value resulting from combustion of the immediately previous kindling or test-
fuel charge. 20.9% shall be used as the baseline ambient air supply oxygen concentration. An example calculation for test fuel additions; if the maximum flue-gas 
oxygen depression from the burning of a preceding fuel charge was 12.5% (i.e., the 
minimum flue-gas oxygen concentration during burning of the fuel load was 8.4% (i.e., 
20.9% - 12.5% = 8.4%) the next fuel charge may only be loaded after the flue-gas oxygen concentration has recovered to at least 17.2% (i.e., (0.70 x 12.5%) + 8.4% = 
17.2%)oxygen but not more than 18.4% oxygen (i.e., (0.8 x 12.5%) + 8.4% = 18.4%). 
5.8.8.1 Alternative Fuel Addition Criteria. The recovery of the peak sum of real time flue-
gas carbon dioxide and carbon monoxide (CO 2 +CO) concentrations back to 
ambient CO 2 +CO concentrations may be used as an alternative to the flue-gas 
oxygen concentration recovery fuel load addition/loading criteria. When using 
CO2 +CO concentrations, test fuel additions shall be placed and burned in the 
fire chamber only after flue-gas CO 2 +CO concentrations have recovered (i.e., 
decreased) back to at least 30% of the maximum flue-gas CO 2 +CO value 
resulting from combustion of the immediately previous test-fuel charge. 
5.8.8.2 Inadequate Coal Bed. If the coal bed remaining after flue-gas oxygen 
concentration has recovered (i.e., increased) to at least 70% of the preceding maximum flue-gas oxygen depression value does not appear to be sufficient or 
adequate for restarting the next test-fuel charge within the allowed 10.0-minute 
fuel-loading period, newspaper and/or kindling may be added and the test-fuel 
charge re-positioned in order to facilitate reasonable ignition of the added test-fuel charge. 
5.8.8.2.1 Additional Newspaper and/or Kindling. The addition of all 
newspaper and/or kindling and the entire test-fuel charge including any additional newspaper and/or fuel added under Section 5.8.8.1 shall be 
completed within 10.0 minutes from the time the first piece of the test-
fuel charge is loaded into the firebox. The weight of all newspaper and/or kindling shall be weighed to the nearest 0.1 lb (0.05 kg), recorded, and 
added to the total test-fuel weight. 5.8.9 Test-Fuel Charge Adjustments. Test-fuel charges may be adjusted (i.e., repositioned) 
once during the burning of each test-fuel charge. The time used to make this adjustment shall not exceed 20 seconds. 
5.8.10 Combustion Air Supply Adjustment. Any and all means for controlling masonry heater 
combustion air supplies may only be adjusted during each of the 10-minute test-fuel 
charging periods. For masonry heaters with air supply controls, or if a masonry heater 
cannot or is not intended to operate at its lowest air supply setting, a permanent instruction label as described in Section 3.4.4 shall be prominently affixed to the masonry 
heater air supply control mechanism. 
5.8.11 Auxiliary Masonry Heater Equipment Operation. Heat exchange blowers (standard or 
optional) sold with the masonry heater shall be operated during all test burns following 
the manufacturers or builder’s written consumer instruction manual instructions. If no manufacturer’s written consumer instruction manual is available, operate the heat exchange blower in the “high” or maximum position. (Automatically operated blowers shall be operated as designed.) Shaker grates, by-pass controls, afterburners, or other 
auxiliary equipment may be adjusted only once during the period that each test-fuel 
charge burns and the adjustment shall be in accordance with the manufacturers or builder’s written instructions. Record and report all adjustments made to auxiliary 
masonry heater equipment during the test period. 
5.8.12 Test Completion. A test period (i.e., a three fuel-crib test-burn period) is completed and 
all sampling and test-period temperature measurements are stopped at the end of the 
first five-minute interval after which the flue-gas oxygen concentrations, as measured by the ESS oxygen sensor, have recovered (i.e., increased) to at least 95% but not more than 97% of the maximum flue-gas oxygen depression value which resulted from 
combustion of the third test-fuel charge. The ESS and any alternative flue-gas sampling 
systems shall continue operation after test completion for a period of time equal to the respective response time, as determined in Section 5.6.8.1, for each sampling train. 
5.8.12.1 Alternative Test Completion Criteria. As with fuel load additions, the 
recovery of the peak sum of real-time flue-gas carbon dioxide and carbon monoxide (CO 2 +CO) concentrations back toward ambient CO 2 +CO 
concentrations may be used as an alternative to the flue-gas oxygen 
concentration recovery for test completion criteria: When using CO 2 +CO 
concentrations, test completion shall occur only after flue-gas CO 2 +CO 
concentrations have recovered (i.e., decreased) back down to at least 3% but not 
more than 5% of the maximum flue-gas CO 2 +CO value resulting from 
combustion of the immediately previous kindling or test-fuel charge. The ESS 
and any alternative flue-gas sampling systems shall continue operation after test completion for a period of time equal to the respective response time, as determined in Section 5.6.8.1, for each sampling train. 
5.8.13 Post-Test Procedures. 
5.8.13.1 Room-Air Velocities. Using a low-velocity-range anemometer within 10 
minutes after test completion, measure and record the room-air velocity within 2 
feet (0.6 meters) of the test masonry heater. Air velocity within 2 feet (0.6 meters) 
of the test masonry heater shall not be more than 50 feet/minute (15 m/min) 
without the masonry heater operating. 
5.8.13.2 Fuel Weight at Test Completion. Within 5 minutes after test completion, 
as defined in Section 5.8.12, the remaining coals and/or unburned fuel and/or ash shall be carefully removed from the firebox and weighed to the nearest 0.1 pounds (0.05 kg). (It is recommended that the coals first be extinguished with 
carbon dioxide.) The weight of these unburned materials and ash shall be subtracted from the total test-burn fuel weight when calculating the test period 
burn rate. A test-burn shall be invalid if less than 90% of the weight of the total 
test-fuel charges plus the kindling weight has been consumed in the masonry heater firebox. 
5.8.13.3 Barometric Pressure at Test Completion. Measure and record the 
barometric pressure within 10 minutes after test period completion. 
5.8.13.4 Leak Check. The ESS shall be leak checked at the maximum test-period 
vacuum level within one hour of sampling completion. Under maximum test-
period vacuum, the ESS sampling system shall not have a leak rate of more than 
2 liters per hour. 
5.8.13.5 Critical-Orifice Flow Rate at Test Completion. Post-test critical-orifice 
flow-rate determinations shall be perf ormed before the ESS is dismantled for 
sample recovery and clean up. Pre-test and post-test critical-orifice flow rate 
measurements shall be within 0.0007 cubic feet (0.02 liters) per minute of each other or the test-burn emissions results shall be invalid. 
5.8.14 ESS Particulate Emissions Sample Processing. Each component of the ESS shall be 
processed as follows: 
5.8.14.1 Filter. The glass-fiber filter (4 inches (102 mm) in diameter) shall be 
removed from the ESS filter housing and placed in a Petri dish for desiccation 
and gravimetric analysis. ESS filters shall be processed in accordance with U.S. Environmental Protection Agency (EPA) Method 5 protocols (Title 40 Code of Federal Regulations, Part 60, Appendix A). 
5.8.14.2 XAD-2 Sorbent-Resin Cartridge. The contents of the XAD-2 sorbent-
resin cartridge shall be extracted in a Soxhlet extractor with dichloromethane 
(methylene chloride) for 24 hours. The extraction solution shall be transferred to 
a clean tared glass beaker and evaporated in a filtered-air dryer at ambient laboratory conditions. The beaker, with dried residue, shall then be desiccated to constant weight (i.e., less than 0.5 mg change within a 2-hour period). The dry 
dichloromethane-extractable residues shall then be weighed to the nearest 0.1 
mg. EPA Method 5 procedures (Title 40 Code of Federal Regulations, Part 60, Appendix A) for desiccation and weighing-time intervals shall be followed for processing the ESS XAD-2 emissions residues. 
5.8.14.2.1 Blanks. Blank values shall be determined for the amount of 
dichloromethane solvent used for extracting the ESS emissions residues 
and these blank values shall be subtracted from the total measured 
emissions residues determined in Section 5.8.14.2. 
5.8.14.3 ESS Hardware Clean-Up. All hardware components which are in the 
flue-gas sample stream (i.e., the stainless-steel probe, the heated sampling line, the filter holder, and all other Teflon® and stainless-steel fittings) through the top 
of the sorbent-resin cartridge, shall be cleaned with a solvent mixture of 50% 
dichloromethane and 50% methanol. The resulting dissolved emissions residues and cleaning solvent solutions shall be placed in tared glass beakers, evaporated 
in an ambient-air dryer, desiccated to constant weight (i.e., less than 0.5 mg 
change within a two hour period), and weighed to the nearest 0.1 mg. 5.8.14.3.1 Blanks. Blank values shall be determined for the amount of each 
solvent used for cleaning ESS components and these blank values shall be subtracted from the total measured emissions residues determined in 
Section 5.8.14.3. 
5.8.14.4 ESS Particulate Emissions Sample Preservation. If ESS samples cannot 
be processed within two hours after test completion, the stainless-steel sampling 
probe, the heated sampling line, the filter holder, and the XAD-2 sorbent-resin cartridge(s) shall be removed from the ESS, placed in a container capable of 
maintaining temperatures of less than 50° F (10° C), and transported to, or stored 
in, the laboratory for processing within 48 hours. 
5.8.14.5 Minimum ESS Particulate Emissions Sample Quantities. For each 
complete test period, the ESS must catch a minimum total particulate material mass of at least 5 mg. Alternatively, the ESS must sample a minimum of 10 cubic feet (275 liters) of flue gases during each test-burn period. If this volume cannot be sampled in the test-burn time period, two ESS samplers must be utilized to 
sample masonry heater emissions simultaneously during each test-burn. If 
emissions factor results from the two ESSs are different by more than 10% of the higher emissions-factor result, the test-burn results shall be invalid. An arithmetic 
average is calculated for test-burn results when two ESSs are utilized in this 
manner and have emissions factor results within 10% of the higher emissions factor amount. 
5.8.14.6 Combustion-Gas Analyzer Calibrations. To correct analytical accuracy 
and drift errors, combustion gas analyzers shall be calibrated using the following three-point calibration procedures before and after the analysis of samples for 
each test period. 
 allow the instrument to operate for a sufficient time to stabilize, as 
recommended by the manufacturer's recommended operating procedures; 
 introduce zero gas into the inlet at a “normal” sample flow rate, and zero the 
analyzer output. Then introduce the high-range calibration gas and span the 
analyzer output; 
 introduce consecutively, in the same manner as described above, the zero 
and mid-range calibration gases, and record the instrument response to each 
when no further change in the analyzer response can be detected; and 
 calculate and plot a linear least-squares calibration curve, forcing, if 
necessary, the curve to pass through the origin. 
5.8.14.7 Sampling Rate Constancy. For the ESS and any alternative flue-gas 
sampling system, calculate the average sampling rate during the entire test period from the data recorded in accordance with Section 5.8.5. Then calculate 
the percentage deviation of each recorded sampling rate from its test period 
average. The sampling rate is adequately constant and valid if the average 
magnitude of the deviations is less than 5% and if no single deviation is larger 
than 10%. 
6.0 CALCULATIONS 
After test completion, data sheets shall be reviewed for completeness and proper equipment operation. 
The data sheets, log books, chain-of-custody, and records maintained by field and laboratory staff shall be reviewed to ensure sample integrity. Test period data sheets shall be used in conjunction with ESS 
particulate samples and flue-gas sample analyses to calculate the test-period burn rate and the particulate emissions factor. 
6.1 Total Test Period and Sampling Time. The total test period sampling time (t tt) in minutes is 
calculated as follows: 
ttt = tc x NT > 25  ° F/% > 95 <97  Equation 6.1.1 
Where: t c = The data-recording cycle (5.0 minutes for this Test Standard). 
NT > 25  ° F/% > 95 <97  = The total number of whole 5.0-minute data-recording cycles 
that occurred between the time when the flue-gas temperature after test-burn ignition first 
exceeded 25 ° F (14° C) more than the pre-test flue-gas temperature (i.e., test period initiation as defined in Section 5.8.4) and the time when the flue-gas oxygen recovery from the third test-fuel charge was at least 95% but not more than 97% (i.e., test period 
completion as defined in Section 5.8.12). 
6.2 Test Period Burn Rate. Burn rate is calculated as follows: 
Burn Rate (kg/hour) = (Fuel Total Weight x 60) / t tt Equation 6.2.1 
Where: Fuel Total Weight = The dry weight of the total fuel, including spacers and kindling added 
during the entire test-burn period minus the remaining unburned materials and ash at the end of 
the test-burn period (kilograms). 
6.3 Particulate Emissions. 
6.3.1 ESS Emissions Factor Using Test Period Oxygen Concentrations. The equation for the 
ESS-particulate emissions factor (EF ESS) presented below utilizes the average flue-gas 
oxygen concentrations measure during the test period. The calculation produces 
reporting units of grams of emissions per dry kilogram of fuel burned (g/kg): 
EFESS = (P m x Fmcc x Mvs) / (ttt x Sr x [(19.3- O 2)/100]) Equation 6.3.1.1 
Where: P m = The total mass of particulate material from the filter, the XAD-2 resin 
cartridge; the probe, and ESS hardware clean-up and rinse solutions (grams). 
Sr = The ESS-sampling rate. The actual, verified, and documented critical orifice 
sampling rate determined in Section 5.7.7.2 (liters per minute). 
Fmcc = The molar carbon content of the fuel (i.e., 42.5 gram moles of carbon per 
dry kilogram of fuel derived from the 51.0% carbon content of Douglas fir). 
Mvs = Molar volume of ideal gases at standard conditions (i.e., 24.06 cubic 
meters per kilogram-mole. 
O2 = The test period average (i.e., percent O 2 in the flue gases). 
19.3 = Sum of dry stoichiometric combustion products (as CO 2 and/or 1/2 CO). 
Note: Multiplying the emission factor by the average burn rate yields the 
particulate emissions rate in grams/hour. 6.3.1.1 Alternate ESS Emission Factor. The ESS Emissions Factor Using the Alternative 
CO2 +CO flue-gas measurements: 
EFESS = (P m x Fmcc x Mvs) / (ttt x Sr x (YCO2 + YCO)) Equation 6.3.1.1.1 
Where: Y CO2 = The test period average of the molar fraction of carbon dioxide in 
the flue gases (i.e., percent CO 2 in the flue gases divided by 100). 
YCO = The test period average of the molar fraction of carbon monoxide 
in the flue gases (i.e., percent CO in the flue gas divided by 100). 
Note: Multiplying the emission factor by the average burn rate 
yields the particulate emissions rate in grams/hour. 
6.3.2 EPA Method-5H Particulate Emissions Factor Equivalent. To convert the ESS Particulate 
Emissions Factor (EF ESS) results from Section 6.3.1 above, to a final Colorado EPA-
Method-5H-Equivalent Emissions Factor (CEF M-5) use Equation 6.3.2.1 as follows: 
CEFM-5 = (0.247 + (0.232 x EF ESS) + (0.00491 x EF ESS2) Equation 6.3.2.1 
Where: EF ESS = The ESS Particulate Emissions Factor (gram/kilogram) from Section 
6.3.1. 
7.0 REPORTING REQUIREMENTS 
Submit both raw and reduced data for all masonry heater tests conducted for Colorado APCD approval. 
All test information and masonry heater drawings submitted for Colorado APCD-approval shall be verified and certified by the Colorado APCD-accredited laboratory that performed the tests being reported. 
Specific reporting requirements are as follows: 
7.1 Masonry Heater Identification. Report masonry heater identification information including 
manufacturer, model, model line, or design and serial number of the masonry heater tested. Also 
include the published installation and operating instructions. 
7.2 Test Facility Information. Report test facility location and test period temperatures and air velocity 
information. 
7.3 Test Equipment Calibration and Audit Information. Report calibration and audit results for the test-
fuel scale, test-fuel moisture meter, analytical balance, and sampling equipment including volume metering systems and flue-gas analyzers. 
7.4 Pretest Information and Conditions. Report all pretest conditions including test-fuel charge 
weights, masonry heater temperatures, and air supply settings. 
7.5 Particulate Emissions Data. Report a summary of test results for all test-burns conducted and the 
arithmetically averaged emission factor for the test-burns used for Colorado APCD approval. Submit copies of all data sheets and other records collected during the testing. Submit examples 
of all calculations performed if not performed in the format presented in Section 6.0. 
7.6 Required Test Report Information and Suggested Format. Test report information requirements 
are presented in the following recommended report format: 
7.6.1 Introduction. 7.6.1.1 Purpose of Test. Colorado APCD-approval or audit. 
7.6.1.2 Masonry Heater Identification. Manufacturer, model name or number, 
catalytic/non-catalytic, emissions control equipment, and any optional equipment. Include a copy of masonry heater installation and operation manuals. 
7.6.1.3 Testing Laboratory. The Colorado APCD approved laboratory name, street and 
mailing address information, telephone number(s), email and contact addresses 
for key personnel, web site address (if existing) and the names of all test 
personnel that performed the testing. A copy of each of the accreditation certificates stipulated in Section 4.1 shall be located in an appendix of the test report. 
7.6.1.4 Test Information. Date masonry heater was received, if factory-built, date 
construction was completed, if site-built, date that each test was conducted, 
sampling methods used, a description of each masonry heater configuration 
tested as required in Section 5.2, and the number of test burns conducted for 
each masonry heater configuration. 
7.6.1.5 Test Method and/or Masonry Heater Operating Protocol Deviations. The report 
shall contain a complete description of any test method or masonry heater operating protocol deviation conducted in the performance of the required test 
procedures and protocols contained in this Test Standard. The report must 
provide detailed rationale explaining the necessity for the deviation(s) and a record of communications conducted for obtaining Colorado APCD approval for 
the deviation(s) undertaken. 
7.6.2 Summary and Discussion of Results. 
7.6.2.1 Table of Results. Test-burn identification number, masonry heater configuration, 
burn rate, particulate emission factor (in U.S. EPA Method 5H equivalents). An example test period summary table is presented in Figure 7.6.2.1. 
7.6.2.2 Summary of Other Data. Test facility conditions, masonry heater surface 
temperature averages, catalyst temperature averages, test-fuel charge weights, 
the average draft pressure measured, and the test-burn durations. 
7.6.2.3 Discussion. Include specific test-burn problems and solutions and rationale for, 
and for not, testing specific configurations like a fuel-elevating grate 
configuration.  
7.6.3 Process Description. 
7.6.3.1 Masonry Heater Dimensions. Firebox height, width, length (or any other pertinent 
dimensions), weight, and hearth area used for calculating fuel-charge weight. 
7.6.3.2 Firebox Internal Assembly Configuration. Include the laboratory-certified 
verification of the construction or assembly drawings, photographs showing air 
supply locations and operating mechanisms, combustion air supply pathway(s), refractory materials and dimensions, catalyst location, baffle and/or by-pass 
configurations and operating mechanisms. 
7.6.3.3 Add-On Emissions Control Equipment. If the masonry heater being submitted for 
Colorado APCD approval utilizes add-on emissions control equipment or a 
catalytic device for reducing masonry heater emissions, provide a list of the brand names and/or sources for all masonry heater components and a complete description of each component including drawings, photographs, and materials 
used in their construction or production. 
7.6.3.4 Masonry Heater Operation Procedures. Air supply settings and any air supply 
and/or fuel-bed/coal-bed adjustments made during the test period. 
7.6.3.5 Test Fuel. Test fuel properties including: the volume, weight, and average dry 
basis moisture content of each fuel load. Also, include photographs of the 
kindling crib and each fuel load crib. 
7.6.4 Sampling Locations. Describe sampling location relative to masonry heater components. 
Include drawings and/or photographs. 
7.6.5 Sampling and Analytical Procedures. Include a brief reference to operational and 
sampling procedures, and optional and alternative procedures used, include details of any parts of the procedures differing from the prescribed methods (e.g., Colorado APCD-
approved alternatives). 
7.6.5.1 Analytical Methods. A brief description of sample recovery and analysis 
procedures. 
7.6.6 Quality Control and Quality Assurance (QC/QA) Procedures and Results. 7.6.6.1 Calibration Records. Description of calibration procedures and results. 
7.6.6.2 Test Method. Test method quality control procedures: leak-checks, volume-meter 
checks and sample-blank analyses. 
7.6.7 Appendices. 
7.6.7.1 Example Calculations. Include complete data tables and accompanying 
examples of all calculations not performed in the format presented in Section 6.0. 
7.6.7.2 Raw Data. Include copies of all original data sheets for sampling records, 
parameter measurements, temperature records, and sample recovery. Include copies of all burn-rate and masonry heater temperature data. 
7.6.7.3 Construction/Assembly Drawings. Masonry heater construction or assembly 
drawings which clearly show all dimensions needed for completing the requirements of Section 3.2. 
7.6.7.4 Sampling and Analytical Procedures. Include detailed description of procedures 
followed by laboratory personnel in conducting the certification tests being reported. 
7.6.7.5 Calibration Records. Details of all calibrations, checks, and audits pertinent to the 
reported test results including dates. 
7.6.7.6 Participants. Test personnel, manufacturer representatives, and regulatory 
observers present during testing. 
7.6.7.7 Sampling and Operation Records. Copies of original records or logs of activities 
not included on raw data sheets (e.g., masonry heater door-open times and 
durations). 
7.6.7.8 Additional Information. Masonry heater manufacturer's written instructions for 
operation of the masonry heater during the reported test periods and copies of 
the production-ready (print-ready) temporary and permanent labels required in Section 3.4. 
7.6.7.9 Laboratory Accreditation Documentation. Copies of each of the accreditation 
certificates stipulated in Section 4.1. 
7.6.8 References Cited in the Report. 
Example Reference Citation Format: 1. Code of Federal Regulations, U.S. EPA Title 40, Part 60, Subpart AAA and 
Appendix A. 
2. Barnett, S. G. and P. G. Fields, 1991, "In-Home Performance of Exempt Pellet 
Stoves in Medford, Oregon," prepared for U.S. Department of Energy, Oregon Department of Energy, Tennessee Valley Authority, and Oregon Department of 
Environmental Quality, July 1991. 
3. Barnett, S. G. and R. R. Roholt, 1990, "In-Home Performance of Certified Pellet 
Stoves in Medford and Klamath Falls, Oregon," prepared for the U.S. Department 
of Energy, 1990. 4. Barnett, S. G., 1990, "Field Performance of Advanced Technology Woodstoves 
in Glens Falls, New York, 1988-1989," for New York State Energy Research and Development Authority, U.S. EPA, Coalition of Northeastern Governors, 
Canadian Combustion Research Laboratory, and the Wood Heating Alliance, 
December 1989. 
____________________________________________________ Editor’s Notes 
History