National Institute for Occupational Safety and Health

National Personal Protective Technology Laboratory 

Procedure No. TEB-APR-STP-0007 Revision: 2.4 Date: 27 January 2023

DETERMINATION OF INHALATION RESISTANCE TEST,

AIR-PURIFYING RESPIRATORS

STANDARD TESTING PROCEDURE (STP)

1. PURPOSE

This document establishes the procedure for ensuring that the inhalation breathing resistance of

chemical cartridge respirators, particulate respirators, gas masks, and tight-fitting powered airpurifying respirators (APRs) submitted for Approval, Extension of Approval, or examined during

Certified Product Audits, meets the minimum inhalation resistance requirements set forth in 42

CFR, Part 84, Subpart I, Section 84.122, Subpart K, Section 84.172, Subpart L, Section 84.203

the Statement of Standard for Chemical, Biological, Radiological and Nuclear (CBRN) FullFacepiece Air-Purifying Respirator (APR) Revision 2 dated 4-4-2003, and the Statement of

Standard for Chemical, Biological, Radiological and Nuclear (CBRN) Air-Purifying Escape

Respirator (APER) dated 9-30-2003.

2. GENERAL

This standard testing procedure (STP) describes the determination of inhalation resistance test for

APRs in sufficient detail that a person knowledgeable in the appropriate technical field can select

equipment with the necessary resolution, conduct the test, and determine whether, or not the

tested system meets the established requirements.

3. EQUIPMENT/MATERIAL

3.1. The list of necessary test equipment and materials follows.

3.1.1. An anthropometric headform or fixture on which to mount the complete 

respirator assembly in the configuration as worn by the user. In addition, fixtures 

are required for mounting a canister only when testing full facepiece APR for 

CBRN and for mounting mouthpiece respirators. 

3.1.2. A means of connecting the headform or test fixture to the flow controller. The 

respirator must be fitted to the test fixture with no leaks.

3.1.3. Vacuum source capable of delivering a minimum of 85 liters per minute (lpm).

3.1.4. Setra Datum 2000 Model 239 digital manometer, or equivalent, with an accuracy 

of ± 0.01%R ± 1 digit. Connect manometer to a pressure tap on the line between 

the flow controller and headform or test fixture with mounted respirator. 

3.1.5. Brooks Instrument Co. model 5853S Mass Flow Controller with Brooks Control 

and Read-out Unit model 0154, or equivalent with an accuracy +/- 0.70%R +/- 

0.20% f.s. 
Procedure No. TEB-APR-STP-0007 Revision: 2.4 Date: 27 January 2023 Page 2 of 7 

3.1.6. Rope caulk, glue gun with hot-melt glue, and beeswax as needed. 

3.1.7. Heating plate, beaker, and small brush as needed. 

4. TESTING REQUIREMENTS AND CONDITIONS

Prior to beginning any testing, confirm that all measuring equipment employed has been

calibrated in accordance with the testing laboratory’s calibration procedure and schedule. All

measuring equipment utilized for this testing must have been calibrated using a method traceable

to recognized international standards when available.

5. PROCEDURE

5.1. Follow individual instruction manuals for set up and maintenance of equipment used in 

this procedure prior to beginning any testing. Any equipment found to be malfunctioning 

must be repaired or replaced and properly set up and calibrated before starting any

testing. 

5.2. Turn on vacuum to start airflow, and using the calibrated mass flow controller, adjust the 

flow to 85 lpm, tolerance +/- 1.4 lpm. 

5.3. Insert the connection of the headform or test fixture to the connection of the resistance 

tester without the respirator mounted. Set the digital manometer to read zero. 

5.4. Disconnect the headform or test fixture from the resistance tester and mount the 

respirator facepiece on the headform or fixture. Using hot-melt glue and beeswax, 

filtering-facepiece respirators are sealed onto a flat plate with a joint for connection to the 

resistance apparatus. A 40 mm female adapter is used to connect the canister for testing 

APR for CBRN. For air purifying escape respirators for CBRN, spread the elastomeric 

neck dam, and pull the hood over the headform. The neck dam should seal tightly around 

the neck of the headform. Mouthpiece type respirators require a special adapter. 

Elatomeric half mask and full-facepiece respirators are carefully mounted on the 

headform to ensure good contact around the entire sealing flange. Rope caulk can be 

used to help seal the critical area around the nose and / or chin for half masks. Be careful 

not to block the mouth of the headform with the chin cup of full facepieces. For each 

particular model, the size that best fits the standard headform should be used. Other 

headforms from different manufacturers are available in the lab to obtain a better seal on 

a particular facepiece if problems are encountered in obtaining a good seal. 

5.5. Insert the connection of the headform or test fixture to the connection of the resistance 

tester.

5.6. Read resistance in inches of water to the nearest hundredth of an inch on the digital 

manometer. Convert inches to millimeters by multiplying by 25.4.

5.7. Record the measurement. 

5.8 Perform the test on three samples.
Procedure No. TEB-APR-STP-0007 Revision: 2.4 Date: 27 January 2023 Page 3 of 7 

6. PASS/FAIL CRITERIA

6.1. The requirements for passing this test are derived from: 42 CFR, Part 84, Subpart I,

Section 84.122, Subpart K, Section 84.172, Subpart L, Section 84.203; the Statement of 

Standard for Chemical, Biological, Radiological and Nuclear (CBRN) Full-Facepiece 

Air-Purifying Respirator (APR) Revision 2 dated 4-4-2003, and the Statement of 

Standard for Chemical, Biological, Radiological and Nuclear (CBRN) Air-Purifying 

Escape Respirator (APER) dated 9-30-2003. 

6.2. The maximum allowable resistance requirements for gas masks are as follows.

Maximum Inhalation Resistance

[Millimeter water column] 

Type of gas mask Initial Final 1

Front-mounted or backmounted (without particulate 

filter)

60 75

Front-mounted or backmounted (with approved 

particulate filter)

70 85

Chin-style (without 

particulate filter)

40 55

Chin-style (with approved 

particulate filter)

65 80

Escape (without particulate 

filter)

60 75

Escape (with approved 

particulate filter)

70 85

1

Measured at end of the service life specified in Tables 5, 6, and 7 of this subpart. 

6.3. The resistance for non-powered, air-purifying particulate respirators upon initial 

inhalation shall not exceed 35 mm water-column height. 
Procedure No. TEB-APR-STP-0007 Revision: 2.4 Date: 27 January 2023 Page 4 of 7 

6.4. The maximum allowable resistance requirements for chemical cartridge respirators are as 

follows. 

Maximum Inhalation Resistance 

[Millimeter water column] 

Type of chemical-cartridge 

respirator

Initial Final 1

Other than single-use vinyl 

chloride respirators: 

For gases, vapors, or gases 

and vapors

40 45

For gases, vapors, or gases 

and vapors, and 

particulates

50 70

Single-use respirator with 

valves: 

For vinyl chloride 20 25

For vinyl chloride and 

particulates

30 45

Single-use respirator 

without valves: 

For vinyl chloride 15 20

For vinyl chloride and 

particulates

25 40

1 Measured at end of service life specified in Table 11 of this subpart.

6.5. The maximum allowable resistance requirements for tight fitting powered air-purifying 

respirators (PAPR) are as follows.

Maximum Inhalation Resistance

[Millimeter water column] 

Type of tight-fitting PAPR Initial Final 1

With HE particulate filter(s) 

only

50 70

With chemical cartridge(s) 

and HE particulate filter(s)

50 70

With chin-style canister and 

HE particulate filter

65 80

With front or back mounted 

canister and HE particulate 

filter

70 85

1

 Measured at end of silica dust test specified in section 84.179. 
Procedure No. TEB-APR-STP-0007 Revision: 2.4 Date: 27 January 2023 Page 5 of 7 

6.6. The maximum allowable resistance requirements for CBRN full facepiece APRs are as 

follows. 

Maximum Inhalation Resistance

[Millimeter water column]

CBRN Full Facepiece AirPurifying Respirators

Initial Final 1

Chin-style canister 65 80

Non facepiece-mounted

canister

70 85

Canister only 50 NA

1 Measured at end of service life

6.7. For CBRN air-purifying escape respirators, the inhalation resistance prior to 

environmental conditioning shall not exceed 70 mm water column. 

7. RECORDS/TEST SHEETS

7.1. Record the test data in a format that shall be stored and retrievable. Data shall be

reported as shown in attached data sheet.

8. ATTACHMENTS

8.1. Attachment A: Sample Inhalation Resistance Test Data Sheet
Procedure No. TEB-APR-STP-0007 Revision: 2.4 Date: 27 January 2023 Page 6 of 7 

8.1 Attachment A: Sample Inhalation Resistance Test Data Sheet
Procedure No. TEB-APR-STP-0007 Revision: 2.4 Date: 27 January 2023 Page 7 of 7 

Revision History

Revision Date Reason for Revision

1.0 7 March 2004 Historic document

1.1 3 June 2005 Update header and format to reflect lab move from Morgantown, 

WV

No changes to method

2.0 30 March 2009 Document name change from RCT-APR-STP-0007, to TEB-APRSTP-0007. Significant rewrite incorporating changes which affect 

form and provide clarification of technical content as follows:

-Addition of alternate method using digital manometer and mass

flowmeter

-Addition of precision and accuracy data for standard and alternate

methods

-New tables added for clarification, removal of obsolete respirator

types and incorporation of CBRN APR, APER and industrial PAPR

types

-New instructions on fitting respirators to headforms and fixtures

-Specifications added to equipment list

2.1 19 September 2012 Update description of mass flow controller called out in 3A1.5. 

Formatting check for web accessibility

2.2 25 March 2014 Modified specification in sections 5.6 and 5.A.4 from “flat 

aluminum plate” to “flat plate”. Editorial change to section 6.1.

2.3 8 March 2019 -Section 3, Updated list of equipment to recognize use of mass flow

meter and electronic, digital manometer (formerly called out as an

alternate procedure).

-Section 4, Updated to current laboratory standards omitting P and A

exercise and practices for lab safety in favor of those employed by

the lab.

-Section 5, Eliminate information on procedure using old

instruments, essentially adopting the “Alternate Procedure”

identified in rev 2.2 as the standard procedure.

-Section 6, Normalized tables used to communicate the pass/fail

values for the various classes of respirators.

2.4 27 January 2023 Removed regulatory references to Subpart KK. Other sections were 

updated with minor editorial formatting, including the sample test 

data sheet.