I just finished reviewing a draft document that a trade group will be asked to vote to sanction the document as it relates to emergency escape respirators. There was a lot of talk about requiring these escape respirators to carry the NIOSH approval of 14G (vs. the more traditional 23C style respirator). There is talk that a respirator with a NIOSH 14G Approval can be used as an escape respirator and this is PARTIALLY true, but comes with a major limitation, as do ALL Air-Purifying Respirators…
| Escape gas mask respirators equipped with full facepieces can also be used for escape from IDLH conditions but not from oxygen-deficient atmospheres. These respirators may be used for escape from contaminant concentrations above the IDLH value provided that the maximum use concentration (MUC) for the canister is not exceeded and adequate oxygen (=19.5%) is present. |
Source: NIOSH Respirator Selection Logic 2004
This Maximum User Concentration (MUC) matter seems to be lost in far too many discussions about proper respiratory protection. The MUC is defined as:
the maximum atmospheric concentration of a hazardous substance from which an employee can be expected to be protected when wearing a respirator, and is determined by the assigned protection factor of the respirator or class of respirators and the exposure limit of the hazardous substance. The MUC can be determined mathematically by multiplying the assigned protection factor specified for a respirator by the required OSHA permissible exposure limit, short-term exposure limit, or ceiling limit. When no OSHA exposure limit is available for a hazardous substance, an employer must determine an MUC on the basis of relevant available information and informed professional judgment.
Simply put, the MUC is: Assigned Protection Factor (APF) X Permissible Exposure Limit (PEL)
I always use the Threshold Limit Valves (TLV) rather than the PELs as they are almost always more protective. Here is a worked example of how we use the MUC will limit an APR, even when used as an Air-Purifying Emergent Respirator (APER).
Full-Face APR has an APF of 50 (Source: 1910.134(d)(3)(i)(A))
Anhydrous Ammonia’s (NH3) PEL is 50 ppm. Its TLV is 25 ppm.
So a 14G Canister can be used to escape an atmosphere of NH3 which is less than 2,500 ppm; or if using the TLV – less than 1,250 ppm.
And like ALL APRs, even those APERs, there must be at least 19.6% Oxygen in the atmosphere.
So yes, a canister that carries the 14G certification can be used for “emergency escape”, but it has LIMITATIONS as an emergency escape respirator and that is the whole truth! How one rectifies knowing that the atmosphere from which they will be escaping can not exceed these limitations is up to those who choose to use an APR as an escape respirator.
Here are a few things to consider:
99.9% of people could not tell the two APRs (14G vs 23C) apart if their lives depended on it (all pun intended).
Nowhere in NIOSH or OSHA literature is it stated that a 14G can be used for escape from IDLH and a 23C can not. Both APR’s have the same limitations and neither is stated to be approved for IDLH escape.
I am going to bet that the vast majority of Respiratory Protection Programs at refrigeration facilities using APR’s will NOT even mention the terms 14G or 23C and the vast majority of these facilities will be using 23C’s, as this is the more traditional style of APR.
OSHA’s Assigned Protection Factors (APF) are the exact same for 14G and 23C, which is a strong indication that the protection provided by 14Gs is not any better than 23C. https://www.osha.gov/laws-regs/regulations/standardnumber/1910/1910.134
As for “recommending” users don 14G NIOSH-approved APRs means that every NH3 refrigeration process would have two (2) brands of APRs to choose from.
In contrast, there are 582 brands/styles of 23C’s rated for NH3 use.
List of 23C’s specific for NH3:
https://www2.cdc.gov/drds/cel/cel_results.asp?startrecord=1&Search=cel_form&maxrecords=50&schedule=23C&contaminant=1&appdatefrom=&appdateto=&powered=&scbatype=&scbause=&privatelabel=
List of 14G’s specific for NH3:
https://www2.cdc.gov/drds/cel/cel_results.asp?startrecord=1&Search=cel_form&maxrecords=50&schedule=14G&contaminant=1&appdatefrom=&appdateto=&powered=&scbatype=&scbause=&privatelabel=
This is NIOSH’s List of Air-purifying escape respirators (APERs):
https://www2a.cdc.gov/drds/cel/cel_cbrn_results.asp?startrecord=1&maxrecords=50&Search=QS&cbrn=cbrn_aper