#	Letters of Interpretation
1	05/31/2023 - 1910.134(d)(1)(ii) - Clarifications for breathing air quality and use
2	12/16/2021 - 1910.134(d)(1) - Respiratory protection against COVID-19 for employees with religiously mandated facial hair
3	01/17/2017 - 1910.134(d)(1)(ii) - OSHA requirements for respirator fit testing with and without facepiece accessories
4	05/14/2012 - 1910.134(d)(1)(iii) - Whether the Respiratory Protection standard requires personal air monitoring to identify and evaluate the respiratory hazards in the workplace.
5	08/05/2011 - 1910.134(d)(1) - OSHA's decision not to provide a religious exemption from the respirator standard.
6	03/07/2003 - 1910.134(d)(1)(i) - Beards may not interfere with face seal;alternative respirators for bearded employees.
7	07/18/2000 - 1910.134(d)(1)(i) - Selection of air purifying respirators for gases and vapors with poor warning properties (diisocyanates)
8	10/01/1999 - 1910.134(d)(1)(ii) - Respirators for voluntary use and cleaning respirators during fit testing.
9	01/29/1999 - 1910.134(d)(1)(ii) - Using combinations of respiratory protection not approved by NIOSH.
10	07/01/1997 - 1910.134(d)(1)(ii) - NIOSH approved respirator during the period of an employee's escape from a chemical release of phosgene.
11	06/20/1997 - 1910.134(d)(1)(ii) - SCBA cylinder interchangeability.
12	01/24/1991 - 1910.134(d)(1)(ii) - Use of non-approved respirators and improper use of approved respirators

#	Regulations
1	04/20/2006 - - Respiratory protection.