NESCAUM Model Regulation for Outdoor Hydronic Heaters 1

Outdoor Hydronic Heater Model Regulation

January 29, 2007

This document contains a model rule to assist state and local agencies in adopting requirements 

that will reduce air pollution from outdoor hydronic heaters (e.g., outdoor wood-fired boilers). It

was developed in cooperation with a number of states and the U.S. Environmental Protection 

Agency (EPA). 

The model regulation is intended to assist government agencies in enacting their own regulations, 

thus are advisory in nature. The purpose of the model rule is to promote cleaner outdoor units 

through common standards across the states that will protect air quality and public health while 

reducing the compliance burden on manufacturers, thus the emphasis on the critical elements 

listed below. By controlling air pollution from these currently unregulated sources, the model 

rule can also serve to level the playing field with previously regulated indoor residential wood 

burning devices. 

Since 1988, the federal government has applied emission standards to most wood-fired residential 

heating devices under its Residential Wood Heater New Source Performance Standards. Outdoor 

wood-fired hydronic heaters, however, are not included in this regulation and do not have to 

comply with other boiler emission requirements. Therefore, unlike other solid fuel devices, these 

pollution sources have no federal regulatory emission standards. With an increase in their use 

and potential health impacts from their emissions, next door neighbors, local communities, and

air quality agencies have a heightened concern about the current and future impacts of these 

devices. 

The various provisions of this model rule are suggestions and examples. To ease the compliance 

burden on manufacturers, NESCAUM recommends that air quality agencies at a minimum adopt 

certain critical elements of the model rule. We highlight these elements in the model rule using 

italicized bold text. The critical elements include:

o Critical definitions

o Emission standards

o Test method procedures

o Certification process

o Labeling requirements

The model rule contains a single method for regulating new units with respect to the critical 

elements and contemplates that states may propose alternative approaches for other provisions.. 

It also provides alternatives for states to consider for regulating previously installed units. Items 

in regular font are recommendations that states should consider, however, given the wide variety 

of local concerns and varying statutory requirements, these sections should be tailored to meet 

individual states’ needs.

Format of this Document: All [bracketed bold] sections require filling in a name, address, 

governmental body, date, or other information. While “[state]” is typically listed for filling in, 

this model rule can be adapted to local agencies that have authority to limit emissions from these 

sources. Italicized bold text identifies critical elements that are recommended for adoption by all 

regulatory agencies undertaking this effort. Footnotes contain explanations or identify issues 

associated with various aspects of the model rule. 
NESCAUM Model Regulation for Outdoor Hydronic Heaters 2

Model Regulation for Outdoor Hydronic Heaters

1. Applicability

A. This Regulation applies statewide.

B. This Regulation applies, in its entirety, to any manufacturer, supplier, 

distributor or person intending to sell, lease, distribute, or market, an outdoor 

hydronic heater in [state] that meets the definition of an outdoor hydronic heater 

and to any person who installs, operates or owns an outdoor hydronic heater.

2. Definitions

A. At Retail – “At Retail” means the sale by a commercial owner of an outdoor 

hydronic heater.

B. Clean wood – “Clean wood” means wood that has no paint, stains, or other 

types of coatings, and wood that has not been treated with, including but not 

limited to copper chromium arsenate, creosote, or pentachlorophenol.

C. Commercial-size heater – “Commercial-size heater” means a heater with a 

rated thermal output greater than 350,000 Btu/hr as rated by the test method 

identified in Section 7C of this Regulation. 

D. Distribute or sell – “Distribute or sell” means to distribute, sell, advertise for 

sale, offer for sale, lease, ship, deliver for shipment, release for shipment, or 

receive and (having so received) deliver or offer to deliver. This term does not 

include the distribution or sale by a manufacturer of an outdoor hydronic 

heater that is installed outside the State.

E. Existing unit – “Existing unit” means an outdoor hydronic heater that is 

available for sale (or is installed and/or operational at the intended location of use)

at retail, wholesale or in the open market as of the promulgation date of this 

Regulation.

F. Heater Efficiency – “Heater efficiency” means the ratio of the delivered useful 

heat output measured by the test methods referenced in Section 7B of this 

Regulation to the calculated heat input of the heater.

G. Installed Units – “Installed units” means any unit sold (or is installed and/or 

operational at the intended location of use) prior to the promulgation of this 

Regulation.

H. Manufactured – “Manufactured” means built and operational, and 

subsequently ready for shipment (whether packaged or not).
NESCAUM Model Regulation for Outdoor Hydronic Heaters 3

I. Manufacturer – “Manufacturer” means any person who constructs or imports 

into the United States an outdoor hydronic heater.

J. Model line – “Model line” means all outdoor hydronic heaters offered for 

distribution or sale by a single manufacturer that are substantially similar in 

design and make as determined by the Department. 

K. New model – “New model” means an outdoor hydronic heater of a new 

design including a new thermal output rating that is not available for sale at retail 

as of the promulgation date.

L. Nuisance – “Nuisance” means [insert state definition of nuisance].

M. Opacity – “Opacity” means the degree to which emissions other than water 

reduce the transmission of light and obscure the view of an object in the

background.

N. Outdoor hydronic heater1 – “Outdoor hydronic heater” means a fuel 

burning device designed to (1) burn wood or other approved solid fuels; (2) that 

the manufacturer specifies for outdoor installation or installation in structures 

not normally occupied by humans (e.g., garages); and (3) heats building space 

and/or water via the distribution, typically through pipes, of a fluid heated in 

the device, typically water or a water/antifreeze mixture. 

O. Particulate matter or PM – “Particulate matter or PM” means total particulate 

matter including PM10 and PM2.5 (condensable and non-condensible fraction).

P. Residential-size heater – “Residential-size heater” means a heater with a 

rated thermal output of 350,000 Btu/hr or less as rated by the test method 

identified in Section 7C of this Regulation.

Q. Sale – “Sale” means the transfer of ownership or control.

R. Similar in all material respects – “Similar in all material respects” means that 

the construction materials, exhaust and inlet air system, and other design features 

are within the allowed tolerances for components identified in Section 6H of this 

Regulation.

S. Startup period – “Startup period” means the time period beginning with 

flame stability after first charge of wood fuel and is no longer than a two hour 

duration. This definition only includes initial startup where no previous coal 

bed exists. This does not include refueling.

 

1

 The critical element is the definition, not the term – therefore states can choose which term they prefer but 

all should use the same definition, which is purposely broad in its scope.
NESCAUM Model Regulation for Outdoor Hydronic Heaters 4

3. Prohibitions

A. Outdoor hydronic heaters that have not been certified, as set forth in 

Section 6, to meet the Phase I or Phase II emission standard, as set forth in 

Section 4 of this Regulation, and are purchased between the rule promulgation 

date and March 31, 2008 must be installed 500 feet or more2 from a property 

line3 and must have a permanent stack extending five feet higher than the peak 

of any roof structure located within 150 feet of the outdoor hydronic heater.4 

B. Effective March 31, 2008 no person shall:

1. Import, supply, distribute or sell, install or allow the installation of any 

outdoor hydronic heater subject to this Regulation unless it has been 

certified as set forth in Section 6 to meet the applicable emission limit set 

forth in Section 4A(1) or 4B(1) of this Regulation. 

2. Outdoor hydronic heaters that meet the applicable 4A(1) or 4B(1) 

emissions standard but not the 4A(2) or 4B(2) requirements must also 

meet the following requirements: must be installed 500 feet or more5 from 

a property line and must have a permanent stack extending five feet higher 

than the peak of any roof structure located within 150 feet of the outdoor 

hydronic heater. 

C. Effective March 31, 2010 no person shall:

1. Import, supply, distribute or sell, install or allow the installation of any 

outdoor hydronic heater subject to this Regulation unless the outdoor 

hydronic heater has been certified, as outlined in Section 6, to meet the 

applicable emission limit set forth in Section 4A(2) or Section 4B(2) of 

this Regulation. 

2. Siting requirements:

a) Units that meet the emission standard defined in Section 

4A(2): No setback or stack height requirement. 

b) Units that meet the emission standard defined in Section 

4B(2): Outdoor hydronic heaters must be installed 300 feet or 

more from a property line and must have a permanent stack 

 

2

 Setback requirements are based on average background conditions of 15 μg/m3. States may need to adjust 

setbacks accordingly, either greater or lesser, based upon a region’s background conditions for fine 

particulate matter.

3

 States may choose to regulate setbacks based upon property lines or based upon the nearest building. 

4

 Setback and stack height requirements should also be codified in building codes.

5

 Setback requirements are based on average background conditions of 15 μg/m3, states may need to adjust 

setbacks accordingly, either greater or lesser, based upon a region’s background conditions for fine 

particulate matter.
NESCAUM Model Regulation for Outdoor Hydronic Heaters 5

extending five feet higher than the peak of any roof structure 

located within 150 feet of the outdoor hydronic heater.6 

D. No person shall operate an outdoor hydronic heater from April 15 to 

September 30 unless the outdoor hydronic heater has been certified, as outlined in 

Section 6, to meet the emission limit set forth in Section 4A(2) or 4B(2) of this 

Regulation. 

E. Prohibited fuels. No person shall burn any of the following items in an 

outdoor hydronic heater:

1. Any wood that does not meet the definition of clean wood;

2. garbage;

3. tires;

4. lawn clippings or yard waste;

5. materials containing plastic;

6. materials containing rubber;

7. waste petroleum products;

8. paints and paint thinners;

9. chemicals;

10. coal;

11. glossy or colored papers;

12. construction and demolition debris;

13. plywood;

14. particleboard; 

15. salt water driftwood;

16. manure;

17. animal carcasses; and

18. asphalt products.

F. Outdoor hydronic heaters must comply with all applicable laws, including but 

not limited to local ordinances.

G. No person shall operate an outdoor hydronic heater in such a manner as to 

create a public or private nuisance. Local Boards of Health may enforce this 

provision according to their general authority to enforce nuisance conditions 

within the State Air Quality Regulations.

4. Particulate Matter Emission Standard for New Units

A. Residential Hydronic Heaters

 

6

 Setback require ments are based on average background conditions of 15 μg/m3. States may need to adjust 

setbacks accordingly, either greater or lesser, based upon a region’s background conditions for fine 

particulate matter.
NESCAUM Model Regulation for Outdoor Hydronic Heaters 6

1. Phase I Emission Standard7 – No person shall distribute or sell, lease, 

import, or install an outdoor hydronic heater after March 31, 2008 unless it 

has been certified to meet a particulate matter emission limit of 0.44 

pounds per million British thermal units (lb/MMBtu) heat input In 

addition, units meeting the Phase I limit must be installed according to the 

setback and stack requirements, as defined in section 3B(2), and the 

seasonal operation limit, as defined in section 3D of this Regulation. 

Compliance with this particulate emission limit shall be determined in 

accordance with the test methods and procedures in Section 6 and 7 of this 

Regulation.

2. Phase II Emission Standard8 – No person shall distribute or sell, 

lease, import, or install an outdoor hydronic heater after March 31, 

2010 unless it has been certified to meet a particulate matter emission 

limit of 0.32 lb/MMBtu heat output. In addition, within each of the 

burn rate categories, no individual test run shall exceed 18 grams per 

hour. Compliance with this particulate emission limit shall be 

determined in accordance with the test method and procedures in 

Section 6 and 7 of this Regulation.

B. Commercial-size Hydronic Heaters

1. Phase I Emission Standard – No person shall distribute or sell, import,

or install a commercially sized outdoor hydronic heater after March 31, 

2008 that has not been tested to meet a particulate matter emission limit of 

0.44 lb/MMBtu heat input In addition, units meeting the Phase I limit 

must be installed according to setback and stack requirement, as defined in 

section 3B(2), and the seasonal operation limit, as defined in section 3D of 

this Regulation. Compliance with this particulate emission limit shall be 

determined in accordance with the test methods and procedures in Section 

6 and Section 7 of this Regulation.

2. Phase II Emission Standard – No person shall distribute or sell, 

import, or install an outdoor hydronic heater after March 31, 2010 that 

has not been certified, as set forth in Section 6, to meet a particulate 

matter emission limit of 0.32 lb/MMBtu heat output. In addition, within 

each of the burn rate categories, no individual test run shall exceed 20 

grams per hour. In addition, units meeting the commercial Phase II 

limit must be installed according to setback and stack requirements, as 

defined in section 3C(2). Compliance with this particulate emission 

limit shall be determined in accordance with the test method and 

procedures in Section 6 and 7 of this Regulation.

 

7

 The Phase I emission rate is based upon a technology transfer analysis. NESCAUM believes that there 

are several units currently on the market that can meet this standard.

8

 The Phase II emission rate is based upon a technology forcing and public health impact analysis. 

NESCAUM believes that there is one unit currently available that can meet this standard.
NESCAUM Model Regulation for Outdoor Hydronic Heaters 7

C. Visible Emission Standard

1. No person shall cause or allow the emission of a smoke plume from 

any outdoor hydronic heater to exceed an average of 20 percent opacity 

for six consecutive minutes in any one-hour period.

2. Exception. Visible emissions may not exceed 40 percent opacity for 

20 consecutive minutes during the startup period of a new fire. This only 

includes initial firing of the unit where no coal bed exists. This exception 

does not apply to refueling.

D. Installed Units9

1. Option A – Time Limit Removal Program. All installed and existing 

outdoor hydronic heaters within the State that do not meet the applicable 

emission limits defined in Section 4A(2) or 4B(2) shall be removed from 

all properties by [date] or rendered permanently inoperable by [date]. It 

shall be a violation of this section for any person on or after [date] to 

possess or operate an outdoor hydronic heater within [state] unless it is 

certified to meet the Phase II emission limits as defined in Section 4 of this 

Regulation, unless it has been rendered permanently inoperable.

2. Option B – Prior Sale or Transfer of Real Property. Prior to the 

completion or consummation of a sale or transfer of any real property on 

or after [date], all existing and/or installed outdoor hydronic heaters that 

do not meet the Phase II emission standard as defined in Section 4 of this 

Regulation shall be replaced, removed, or rendered permanently 

inoperable.

3. Option C – Setback and Stack Height Requirement for Installed Units. 

All existing and installed outdoor hydronic heaters that do not meet the 

Phase II emission standard as defined in Section 4 if this Regulation 

within the State shall either meet the Phase I setback and stack height 

requirements, as defined in Section 4A of this regulation, or be removed 

from all properties by [date] or rendered permanently inoperable by 

[date]. The outdoor hydronic heater must be installed 500 feet or more 

from a property line. The outdoor hydronic heater must have a permanent 

stack extending five feet higher than the peak of any roof structure located 

within 150 feet of the outdoor hydronic heater.

5. Fuel Requirements

 

9

 The section for installed units is intended for states that wish to address units installed prior to rule 

promulgation. States may choose to implement one of the three options or combinations of options or defer 

to local governments to address existing outdoor hydronic heaters.
NESCAUM Model Regulation for Outdoor Hydronic Heaters 8

A. No person that operates an outdoor hydronic heater shall use a fuel other 

than the following:

1. Clean wood;

2. Wood pellets made from clean wood;

3. Home heating oil in compliance with the applicable sulfur content 

limit or natural gas may be used as starter fuels for dual-fired outdoor 

hydronic heaters; and

4. Other fuels as approved by the Department.

6. Certification10

A. Certification Requirement

1. No person shall supply, distribute, sell, lease, offer for sale, or allow 

the installation of an outdoor hydronic heater in [state] unless the 

Department, or equivalent authority approved by [state], has issued a 

certification to the manufacturer that the outdoor hydronic heater, or 

model line to which it belongs, complies with the particulate matter 

standard in Section 4 of this Regulation. A certification shall be valid for 

a period of five years unless revoked by the Department.

2. Certifications for units that meet the Phase I emission limit but not the 

Phase II as defined in Section 4 of this Regulation will expire prior to the 

compliance date for Phase II as defined in Section 3C.

B. Certification Procedure: For each model line, units must demonstrate 

compliance with the applicable emission standard, which may be determined 

based on testing of a representative number of units within a model line. In order 

for an outdoor hydronic heater or new model line to obtain a certification by the 

State, the manufacturer of any such heater shall conduct testing via EPA’s 

Environmental Technology Verification Program and submit the results to the 

State for its review and approval, or via an alternative program approved by the 

State.11

C. Issuance of Certification: The Department shall issue a certificate of 

compliance for a model line if it determines, based on the information submitted 

by the applicant and any other relevant information available to them, that:

1. A valid certification test has demonstrated that a representative unit of 

a model line complies with the applicable particulate matter emission limit 

 

10 States must adopt a certification program, however, states may revise this section as necessary.

11 Appendix A contains a draft of a state certification program.
NESCAUM Model Regulation for Outdoor Hydronic Heaters 9

as defined in Section 4 of this Regulation. To be valid, a certification test 

must be:

a) Announced in accordance with Section 7E of this Regulation;

b) Conducted by an accredited testing facility in accordance with 

Section 6F of this Regulation;

c) Conducted on a unit similar in all materials respects to other 

units of the model line to be certified; and 

d) Conducted in accordance with the test methods and procedures 

specified in Section 7B of this Regulation.

2. A statement shall be made by the manufacturer to the effect that any 

tolerances for materials or components listed in Section 6H of this 

Regulation that are different than those specified in the applicable model 

specifications may not reasonably be anticipated to cause units within the 

model line to exceed the applicable emission limit.

D. Denial of Certification – Upon denying a certification under this paragraph, 

the Department or its designee shall give written notice to the manufacturer 

setting forth the basis for its determination.

E. Quality Assurance Program – For each certified model line, the manufacturer 

or its designee shall conduct a quality assurance program that, at a minimum, 

includes the following requirements:

1. The manufacturer or authorized representative shall inspect one in 

every 150 units produced within a model line to determine that the units 

are within applicable tolerances for all components that affect emissions as 

listed in Section 6H of this Regulation.

2. The manufacturer or authorized representative shall conduct an 

emission test on a randomly selected unit produced within a model line on 

the following schedule: 

If certification If yearly production per model is:

test results were: <500 total production =500 total production

70% or less of the 

PM emission 

standard

When directed by the 

State not to exceed one 

of every 1,000 units

Every 1,000 units or 

triennially (whichever 

is more frequent)

30% or less of the 

PM emission 

standard

Every 2,000 units Every 2,000 units or 

annually (whichever is 

more frequent)
NESCAUM Model Regulation for Outdoor Hydronic Heaters 10

3. The emission test shall be conducted in conformity with Section 7B of 

this Regulation. The manufacturer shall notify the State by US mail that 

an emissions test required pursuant to this paragraph will be conducted 

within one week of mailing the notification.

4. If the manufacturer uses a different material for the firebox, firebox 

component, or hydronic heating mechanism than the one used for 

certification testing, the first test shall be performed before 500 units are 

produced. The manufacturer shall submit a report of the results of this 

emission test to the State within 45 days of completion of testing. 

F. Approved Test Facilities – An accredited laboratory shall conduct all of the 

testing, test reporting, and product inspection requirements of this Regulation. 

Emission testing for certification shall be conducted by an independent contractor 

who has no conflict of interest or financial gain in the outcome of the testing.

G. Laboratory Accreditation Requirements – In order to qualify for accreditation 

under this Regulation, a test laboratory shall first be accredited:

1. by the U.S. Environmental Protection Agency (EPA) for testing woodburning residential space heaters in accordance with 40 CFR Part 60,

Subpart AAA, Section 60.535;

2. 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

3. by a nationally recognized accreditation body to ISO/IEC 17025, 

General Requirements for the Competence of Testing and Calibration 

Laboratories. 

4. The nationally recognized accrediting body itself shall be accredited 

to, and operate under ISO Guide 58 (Calibration and Testing Laboratory 

Accreditation Systems – General Requirements for Operation and 

Recognition), and

5. by a nationally recognized accreditation body to the American Society 

for Testing and Materials (ASTM) Standard Practice D7036-04; 

Competence of Air Emission Testing Bodies.

H. Laboratory Audits – Laboratory operations and recordkeeping audits by ANSI 

or another nationally recognized accrediting body shall be conducted at least 

annually and the audits shall be specific to the laboratory operations directly 

responsible for conducting the testing, certification, and inspection services 
NESCAUM Model Regulation for Outdoor Hydronic Heaters 11

required by this Regulation. Results of the audit will be provided to [state] on 

March 1st of each year for its review.

I. Re-certification – The Department shall determine the frequency of 

certification testing of an outdoor hydronic heater or model line, with a minimum 

frequency of at least once in every five years of the outdoor hydronic heater or 

model line made available at retail.

J. Change in Design Parameter – A model line must be re-certified whenever 

any change is made in the design that is presumed to affect the particulate 

emission rate for that model line. Changes that are presumed to affect particulate 

emission rates for model lines include:

1. Tolerance changes: any change in the indicated tolerances of any of 

the following components is presumed to affect particulate emission rates 

if that change exceeds ±0.64 cm (± 1⁄4 inch) for any linear dimension and 

±5 percent for any cross-sectional area relating to air introduction systems

and catalyst bypass gaps unless other dimensions and cross-sectional areas 

are previously approved by the State;

2. Firebox: dimensions;

3. Air inductions systems: cross–sectional area of restrictive air inlets, 

outlets and location, and method of control;

4. Baffles: dimensions and location;

5. Refractory/insulation: dimensions and location;

6. Catalyst: dimensions and location;

7. Catalyst bypass mechanism: dimensions, cross-sectional area, and 

location;

8. Flue gas exit: dimension and location;

9. Door and catalyst bypass gaskets: dimension and fit;

10. Outer shielding and coverings: dimension and location;

11. Fuel feed system;

12. Forced air combustion system: location and horsepower of blower 

motors and fan blade size.
NESCAUM Model Regulation for Outdoor Hydronic Heaters 12

K. Material changes – Any change in the materials used for the following 

components is presumed to affect emissions:

1. refractory/insulation;

2. door and catalyst bypass gaskets;

3. for catalyst equipped units – change in catalyst make, model or 

composition;

4. heat exchanger;

5. heating fluids.

L. Revocation of certification – Certification of an outdoor hydronic heater may 

be revoked by the Department based on any of the following:

1. The outdoor hydronic heater does not meet the applicable particulate 

emission limit in Section 4 of this Regulation based on test data from 

retesting of the original unit used for certification testing;

2. A finding that the certification test was not valid;

3. A finding that the unit does not comply with the labeling requirements 

detailed in Section 9 of this Regulation;

4. Failure to comply with recordkeeping and reporting requirements 

detailed in Section 8 of this Regulation;

5. Physical examination showing that more than twenty percent of 

production units inspected are not similar in all material respects to the 

model used for certification testing;

6. Failure of the manufacturer to conduct a quality assurance program as 

detailed in Section 6E of this Regulation.

M. Outdoor hydronic heaters certified to meet the Phase I emission limit, as 

defined in Sections 4A(1) and 4B(1) of this Regulation, shall be automatically 

revoked effective March 31, 2010.

7. Testing Requirements

A. Test Facility
NESCAUM Model Regulation for Outdoor Hydronic Heaters 13

1. All emissions testing shall be conducted by an accredited, qualified, 

and independent testing consultant as defined in Section 6E who has no 

conflict of interest or financi al gain in the outcome of the testing. 

2. Manufacturers of the outdoor hydronic heaters shall not involve 

themselves in the conduct of any emissions testing under Section 7 of 

this Regulation nor the operation of the unit being tested, once actual 

sampling has begun.

B. Test Method – Emission tests shall be conducted using one of the following:

1. EPA Method 28 OWHH Test Method, or

2. An alternative method approved by the Department. 

C. Btu Rating – Testing to determine MMBtu/hr shall be conducted according 

to the test method defined in Section 7B of this Regulation. This testing 

determines the categorization of an outdoor hydronic heater as a commercial or 

residential-sized unit.

D. Notice to State – The manufacturer of the outdoor hydronic heater shall 

provide notice to the Department at least 60 days prior to any emission test to 

allow the Department to have an opportunity to have an observer present 

during the conduction of the test. If requested by the State, the manufacturer 

shall pay all expenses to allow for the observation of the test by a State 

representative.

E. Test Protocols – If there is any deviation from the test method defined in 

Section 7B(1) of this Regulation, the manufacturer of the outdoor hydronic 

heater shall provide the Department with a test protocol for approval by the 

Department in accordance with the testing requirements in Section 7 of this 

Regulation 45 days prior to the emission testing for certification.

8. Notification by Manufacturers

A. By March 1st each year, and as outdoor hydronic heaters are certified, 

manufacturers shall provide the following information in writing to any person to 

whom the manufacturer has distributed or sold or intends to distribute or sell, or 

for installation:

1. A list of all models of outdoor hydronic heaters that it manufactures; 

and

2. A list of models that have received certification to meet the particulate 

matter emission standards and certification requirements set forth in 

Section 4A and 4B respectively.
NESCAUM Model Regulation for Outdoor Hydronic Heaters 14

B. By March 1st of each year, a copy of all written information necessary to 

demonstrate compliance of Section 4, Section 6, and Section 8 of this Regulation 

shall be submitted to the Department.

C. Within one month of promulgation of this Regulation, manufacturers and 

distributors of outdoor hydronic heaters sha ll notify all persons who purchase or 

plan to purchase an outdoor hydronic heater of the requirements in Section 3, 

Section 4, and Section 5 of this Regulation.

D. Manufacturers must notify owners of installed units of the requirements of 

this Regulation.

9. Labeling Requirements for Manufacturer

A. Permanent label – Within three months of promulgation of this Regulation, 

any outdoor hydronic heater introduced into commerce into [state] shall meet 

the following label requirements:

1. Have a permanent label that shall:

a) Be permanently affixed in a readily visible or accessible 

location;

b) Be at least 31⁄2 inches long by 3 inches wide;

c) Be made of a material expected to last the lifetime of the unit;

d) Present required information in a manner so that it is likely 

to remain legible for the lifetime of the unit;

e) Be affixed in such a manner that it cannot be removed from 

the appliance without damage to the label.

f) The permanent label may be combined with any other label, 

as long as the required information is displayed, and the 

integrity of the permanent label is not compromised. 

2. The permanent label shall display the following information:

a) Month and year of manufacture;

b) Model number or name;

c) Serial number;
NESCAUM Model Regulation for Outdoor Hydronic Heaters 15

d) Thermal output rating in MMBtu/hr;

e) Date of certification;

f) Results of emissions standard testing in grams per hour and 

lb/MMBtu input and output for respective Phase I and Phase 

II certification testing as defined in Section 4 of this 

Regulation.

B. Required Labeling – each unit shall prominently display the following 

language on the outdoor hydronic heater:

1. Language stating, “It is unlawful to burn garbage, treated or painted 

wood, coal, tires, plastic and plastic products, rubber products, yard waste, 

lawn clippings, glossy or colored papers, construction and demolition 

debris, plywood, particleboard, salt water driftwood, manure, animal 

carcasses, asphalt products, waste petroleum products, paints, chemicals or 

any substance that normally emits dense smoke or obnoxious odors.”

2. For units equipped with catalytic combustors, the following statement 

shall appear on the permanent label: “This unit contains a catalytic 

combustor that needs periodic inspection and replacement for proper 

operation. Consult owner’s manual for further information. It is against 

the law to operate this unit in a manner inconsistent with operating 

instructions in the owner’s manual, or if the catalytic element is 

deactivated or removed.”

C. Temporary Labeling – All units shall have attached to them a temporary 

label that shall contain the following:

1. A statement indicating the compliance status of the model;

2. A graphic representation of the composite particulate matter 

emission rate as determined in the certification test, or as determined by 

the State;

3. A graphic representation of the efficiency of the model;

4. A numerical expression of the heat output range in British thermal 

units per hour (Btu/hr) rounded to the nearest 100 Btu/hr;

5. Statements regarding the importance of proper operation and 

maintenance;

6. The manufacturer and identification of the model.
NESCAUM Model Regulation for Outdoor Hydronic Heaters 16

7. The temporary label shall:

a) Not be combined with any other label or information;

b) Be attached to the unit in such a manner that it can be 

easily removed by the consumer.

D. Owner’s Manual – Each outdoor hydronic heater offered for sale or lease 

must be accompanied by an owner’s manual that shall contain all the 

information listed below:

1. Proper thermal output capacity for matching with the building’s 

thermal demands;

2. Proper installation information;

3. Operation and maintenance information;

4. Wood loading procedures, recommendations on wood selection, and 

warnings on improper fuels;

5. Fire starting procedures;

6. Proper use of air flow devices, if applicable;

7. Ash removal procedures;

8. For catalytic models, information pertaining to maintaining catalyst 

performance, maintenance procedures, procedures for determining 

catalyst failure or deterioration, procedures replacement, and 

information on warranty rights.

9. Persons operating this hydronic heater are responsible for operation 

of the hydronic heater so as not to cause a nuisance condition. 

Manufacturer guarantees, however, that proper operation of the outdoor 

hydronic heater in accordance with manufacturer’s operating and 

maintenance procedures will not create a nuisance condition.

10. Notice to Buyers

A. No outdoor hydronic heater subject to the requirements of this Regulation 

shall be offered, sold, offered for retail sale, or leased within the State unless prior 

to any sales or lease agreement, the seller or dealer provides the prospective buyer 

or lessee with a copy of the Department’s Regulation and a written notice stating 

that:
NESCAUM Model Regulation for Outdoor Hydronic Heaters 17

1. It is unlawful to burn garbage, treated or painted wood, coal, plastic 

and plastic products, rubber products, yard waste, lawn clippings, glossy 

or colored papers, construction and demolition debris, plywood, 

particleboard, salt water driftwood, manure, animal carcasses, asphalt 

products, waste petroleum products, paints, chemicals or any substance 

that normally emits dense smoke or obnoxious odors;

2. Installation of an outdoor hydronic heater may be subject to other 

applicable State and local stack height and setback requirements;

3. Use of an outdoor hydronic heater that meets the distance and stack 

height requirements provided in Section 3 of this Regulation may not be 

adequate in some areas due to terrain that could render the operation of an 

outdoor hydronic heater to be a nuisance or public health hazard; and

4. Gives the specific results of the average and maximum emission rates 

of particulate matter for the outdoor hydronic heater in grams per hour per 

the testing conducted in Section 7 of this Regulation and the average 

delivered heating efficiency as found in the test reports that were used for 

certification of the units as detailed in Section 7 of this Regulation.

B. The written notice specified above shall be signed by the buyer or lessee at the 

time of purchase or lease to indicate receipt of notification of the requirements of 

this Section. Within seven days of making delivery of the outdoor hydronic 

heater into the possession of the buyer or lessee, the seller or dealer shall mail or 

otherwise provide a copy of the signed notice specified above to the Department. 

Said notice shall contain the name; address; telephone number of both the seller 

or dealer and the buyer or lessee; the location where the outdoor hydronic heater 

will be installed; and the make and model of the outdoor hydronic heater.

11. Nuisance Conditions 

A. No person shall cause or allow emissions of air contaminants to the outdoor 

atmosphere of such quantity, characteristic or duration that are injurious to 

human, plant or animal life or to property, or that unreasonably interfere with the 

comfortable enjoyment of life or property. Notwithstanding the existence of 

specific air quality standards or emission limits, this prohibition applies, but is not 

limited to, any particulate, fume, gas, mist, odor, smoke, vapor, toxic, or 

deleterious emission, either alone or in combination with others. 
NESCAUM Model Regulation for Outdoor Hydronic Heaters 18

Appendix A – State Certification Application information

1. State Certification Program: Manufacturers requesting certification shall submit an 

application to the State. An application shall consist of two complete copies of 

applications and attachments. The application must be signed by the manufacturer or an 

authorized representative, and shall contain the following:

A. The model name and/or design number.

B. Four color photographs of the tested unit, showing the front, back and both 

sides.

C. Engineering drawings and specifications of components that may affect 

emissions, including specifications for each component listed in Section 6H of 

this Regulation. Manufacturers may use complete assembly or design drawings 

that have been prepared for other purposes, but should designate on the drawings 

the dimensions of each component listed in Section 6H of this Regulation. 

Manufacturers shall identify tolerances of components of the tested unit listed in 

Section 6H of this Regulation that are different from those specified in that 

paragraph, and show that such tolerances may not reasonably be anticipated to 

cause outdoor hydronic heaters in the model line to exceed the applicable 

emission limit.

D. A statement whether the firebox or any firebox component will be composed 

of material different from the material used for the emission certification testing 

and description of any such differences.

E. For applications to certify a model line for use with catalytic devices, a 

statement describing the manufacturers program to ensure consistency in the size 

of any gap in the catalyst bypass mechanism.

F. A written report of the results of such tests, including a detailed description of 

the operating conditions of the heater during the tests, for review and approval by 

the Department or its designee, which shall include all documentation pertaining 

to a valid certification test, including the complete test report and, for all test runs, 

raw data sheets, laboratory technician notes, calculations, and test results. 

Documentation shall include the items specified in the applicable test methods. 

G. For units using catalysts, a copy of the catalytic combustor warranty.

H. A statement that the manufacturer will conduct a quality assurance program 

for the model line that satisfies the requirements of Section 6E of this Regulation. 

I. A statement describing how the tested unit was sealed by the laboratory after 

completion of the certification testing.
NESCAUM Model Regulation for Outdoor Hydronic Heaters 19

J. A statement that the manufacturer will notify the certified laboratory, if the 

application for certification is granted, within thirty days of notification from the 

State.

K. Statements that the outdoor hydronic heater offered for sale or lease will be:

1. Similar in all material respects to the unit submitted for certification 

testing, and

2. Will be labeled as defined in Section 9 of this Regulation.

L. A statement that the manufacturer will comply with the recordkeeping and 

reporting requirements detailed in Section 8 of this Regulation.

M. A written statement estimating the numbers of outdoor hydronic heaters that 

the manufacturer will produce in the first three production years. 

N. A statement that the manufacturer has entered into a contract with an 

accredited laboratory as defined in Section 6F of this Regulation that will:

1. Conduct random compliance audit testing at no cost to the 

manufacturer, if the State selects that laboratory to conduct the test, or

2. Pay the manufacturer the reasonable cost of a random compliance 

audit test, if the State selects any other laboratory to conduct the test.

O. At the beginning of each test run in a certification test series, four photographs 

of the fuel load: one before and one after it is placed in the unit. One of the 

photographs shall show the front view of the load and the other shall show the 

side view.