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National Institute for Occupational Safety and Health

National Personal Protective Technology Laboratory 

626 Cochrans Mill Road 

Pittsburgh, PA 15236

Procedure No. CVB-APR-STP-0087 Revision: 0.0 Date: 23 March 2020

DETERMINATION OF LOW FLOW WARNING DEVICE VISIBILITY,

FOR POWERED AIR-PURIFYING RESPIRATORS (PAPR) SERIES PAPR100

STANDARD TESTING PROCEDURE (STP)

1. PURPOSE

This test establishes the procedure for ensuring that the level of protection provided by the low

flow warning device visibility requirement for powered air-purifying respirators (PAPR), series

PAPR100, meet the minimum requirements set forth in 42 CFR Part 84, Subpart K, 84.171(j)(1).

2. GENERAL

This STP describes the Determination of Low Flow Warning Device Visibility, For Powered AirPurifying Respirators, Series PAPR100, test procedure 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 product passes the test.

3. EQUIPMENT/MATERIAL

None

4. TESTING REQUIREMENTS AND CONDITIONS

4.1. 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.

4.2. Determination of Low Flow Warning Device Visibility will be completed for any 

PAPR100 respirator with a visual low flow warning device. 

4.3. Testing shall be conducted on as-received respirators at 25 ± 2.5 degrees Celsius (°C) and 

adhere to User’s Instructions.

4.4. One complete respirator system will be evaluated for low flow warning device visibility. 

5. PROCEDURE

5.1. Prior to any testing, the respirator shall be evaluated per the user check instructions in the 

User’s Manual to ensure that the low flow warning(s) activate as designed.

5.2. The visibility test will be conducted with a fully assembled PAPR system. The warning 

device shall be appropriately positioned and colored such that any warning is obvious and 
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Procedure No. CVB-APR-STP-0087 Revision: 0.0 Date: 23 March 2020 Page 2 of 3 

easily understandable to the wearer.

5.3. The laboratory technician performing the testing will select three volunteer subjects to 

don the respirator. 

5.3.1. User’s Instructions regarding the low flow warning device shall be reviewed by 

the wearer of the PAPR100. 

5.3.2. The respirator shall be cleaned prior to donning for each wearer, per the User’s 

Instructions. 

5.4. Restrict flow to the respirator to activate the low flow warning device. Take care to not 

jar, shift, or otherwise obstruct the wearer’s view of the respirator.

5.5. All wearers of the respirator shall give a verbal description regarding their ability to see 

the visual indication of low flow, whether or not the warning device is visible, and any 

qualitative additions they may offer. Qualitative additions shall not be solicited from the 

subject, but shall be noted if they are offered. Qualitative observations may, and should 

be provided as part of the test report, so long as subject anonymity is maintained in so 

doing. 

6. PASS/FAIL CRITERIA

6.1. The requirement for passing this test is set forth in 42 CFR Part 84, Subpart K, Section 

81.171(j)(1). 

6.1.1. A pass is defined as all three wearers of the respirator confirming visibility of the 

low flow warning device. 

6.1.2. A fail is defined as one or more wearers of the respirator denying visibility of the 

low flow warning device.

7. RECORDS/TEST SHEETS

7.1. Record the test data in a format that shall be stored and retrievable.
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Procedure No. CVB-APR-STP-0087 Revision: 0.0 Date: 23 March 2020 Page 3 of 3 

Revision History

Revision Date Reason for Revision

0.0 23 March 2020 Original Release