- Air Purifying (Negative Pressure) and Powered Air Purifying (Positive Pressure)
- Supplied Air – From SCBA (Self Contained Breathing Apparatus) or from Breathing Air Cylinders (or other approved means) or Supplied by a Air-Line.
The intent is to reduce, or prevent, the inhalation of contaminants.
You cannot wear an Air Purifying Respirator:
- For exposure to unknown substances.
- If the levels of known substance the Respirator use is approved for if the substance is at levels Immediately Dangerous to Life and Health (IDLH)
- If the levels of known substance the Respirator use is approved for is beyond the Maximum Use Concentrations (MUC) for the Respirator (i.e. the use is permitted for the substance, but the Concentration of the Substance Exceeds the ability of the Respirator).
- If there there is less than 19.5% Oxygen, Respirators Filter Air, they do not supply oxygen.
Elastomeric Respirators with Organic Vapor Cartridges for use in a Benzene Exposure.
- ½ Face Air Purifying Respirator has an Assigned Protection Factor (APF) of 10.
- Full Face Air Purifying Respirator has an Assigned Protection Factor of 50.
Employee Permissible Exposure Limit (PEL) is 1 ppm Benzene (Time Weighted Average over 8 Hours) without a Respirator.
- Employees, wearing a ½ Face Respirator can be exposed up to 10 ppm since the MUC = APF 10 x PEL 1
- Employees, wearing a Full Face Respirator can be exposed up to 50 ppm since the MUC = APF 50 x PEL 1
These values are calculated to lower the exposure in the Mask to the PEL or Less.
With Non-Powered Air Purifying Respirators Slight leakage occurs, even with Tight Fitting Facepieces, due to the Negative Pressure nature of the Air Filtration, a lower Pressure inside the Mask exists while the user is Breathing-In. To Eliminate this issue, Powered Air Purifying Respirators are available that pull air through the filters and injects it under slight Positive Pressure in the Facepiece, therefore any leakage is to the outside of the mask and prohibits the contaminant from entering.
There are Substance Specific Standards that do not adhere to the MUC Calculations. For Example, OSHA says for Benzene that the MUC is Less than or equal to 100 ppm wearing a Full Face Powered Air Purifying Respirator with the specified Canister and Canister Change-out Frequency. Yet the APR is listed as 1000. You cannot apply the MUC = APF x PEL for this application, as the MUC would INCORRECTLY be 1000 X 1 or 1000 ppm which is clearly too high.
Nevertheless, Powered Air Purifying Respirators should prevent infiltration of the substance into the mask, leakage is always towards the outside of the mask.
Respirators come as Tight Fitting and Disposable Filtering Facepieces. Tight Fitting Respirators are Elastomeric Half Face and Full Face Respirators made from Rubber, Silicone, etc. These Respirators generally utilize Removable Disposable Cartridges and Filters, but Disposable Half Face Elastomeric Respirators Exist.
There Are Surgical Masks, and Disposable Filtering Facepiece Respirators, they are not the same.
OSHA Link: Respiratory Infection Control: Respirators Versus Surgical Masks
Surgical Masks Help Protect the patient, or others in the area, from the wearer’s Infectious Cough or Sneeze Droplets, and help to protect from the wearer mindlessly placing their fingers in their mouth or nose.
Disposable Filtering Facepiece Respirators help protect the wearer from Infectious Cough or Sneeze Droplets from others (and help to protect from the wearer mindlessly placing their fingers in their mouth or nose).
Something has bothered me, in terms of Disposable Filtering Facepiece Respirators, and I see that the issue is addressed in a 3M Corporation (Maker of among other things, Respiratory Protection Equipment) FAQ Sheet and Links for the Influenza Virus.
3M Link to PDF: Frequently Asked Questions: Considerations for the use of Respiratory Protection for Exposures to the Influenza Virus:
Can a valved respirator be used for protection from the virus that causes influenza?
A valved respirator is designed to allow for easy exhalation through a one-way exhalation valve. If a person is wearing a respirator to help reduce his or her exposure to airborne viruses, a respirator with an exhalation valve would be acceptable. It would not be acceptable for someone to wear a valved respirator if they have a/are suspected/probable/confirmed case of swine flu, as they would be exhaling into the environment. For other situations where healthcare workers are required to wear a respirator the use of a valved respirator must be in accordance with national guidelines. For example, in some regions of the world such as the U.S. and Canada, it is not acceptable for a healthcare worker to wear a valved respirator in a situation requiring a sterile environment, such as the operating room.
In a world desperate for Respiratory Protection Products, DO NOT GIVE KNOWN OR SUSPECTED POSITIVE COVID-19 (or any other Communicable Pathogen) PATIENTS FILTERING FACEPIECE RESPIRATORS WITH EXHAUST VALVES, they will readily exhale the pathogen into the environment, negating to a large degree their reason for being given the respirator to begin with. I’ve not seen this, but it is a concern.
As respirator models/styles are perhaps commingled due to short supplies, bear in mind the following, from above: in some regions of the world such as the U.S. and Canada, it is not acceptable for a healthcare worker to wear a valved respirator in a situation requiring a sterile environment, such as the operating room.
OSHA Link: Standard Interpretations
1. Definition of a single use and negative pressure respirator
Response: OSHA’s Respiratory Protection Standard does not define “single use” respirators. The “single use respirator” used for protection from the H1N1 Influenza virus usually refers to a disposable N95 filtering facepiece respirator. Disposable respirators are not required to be discarded at the end of each task, but discarded when they are no longer in their original working condition, whether its condition results from contamination, structural defects, or wear. A negative pressure respirator means any tight-fitting respirator in which the air pressure inside the facepiece is negative during inhalation with respect to the ambient air pressure outside the respirator. The disposable N95 filtering facepiece respirator is a negative pressure respirator.
2. Is fit-testing required for the disposable N95 filtering facepiece respirator used for protection from the H1N1 virus?
Response: The respiratory protection standard, 29 CFR 1910.134, under paragraph (f)(2), requires fit testing for all employees using tight fitting respirators including filtering facepiece respirators (e.g., disposable N95 respirators). The fit test must be performed before the respirator is used in the workplace and must be repeated at least annually and whenever a different respirator facepiece is used or a change in the employee’s physical condition could affect the respirator fit.
3. Is a written respiratory protection program needed for the disposable N95 respirator?
Response: Yes. A written respiratory protection program, in accordance with 29 CFR 1910.134(c) (including medical evaluation, training, and fit testing), is required in any workplace where respirators (including disposable N95 filtering facepiece respirators) are necessary to protect the health of the employee or whenever respirators are required by the employer.
4. Is there any circumstance when the disposable N95 respirator can be used without fit testing?
Response: The voluntary use of respirators in atmospheres which are not hazardous does not require the respirator to be fit tested or the wearer to maintain a tight fit.
5. What are the requirements for the disposable N95 filtering facepiece respirator when it is used for protection from the H1N1 virus?
Response: As stated above, the use of disposable N95 filtering facepiece respirators in the workplace must be included in an employer’s written respiratory protection program. The respirator program in 29 CFR 1910.134(c) includes medical evaluation, training, and fit testing, and is required in any workplace where respirators (including disposable N95 filtering facepiece respirators) are necessary to protect the health of the employee or whenever respirators are required by the employer.
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