What protection factors actually mean when wearing RPE

RPE (Respiratory Protective Equipment) is worn in the workplace so that workers levels of exposure to contaminants such as particulates, gasses and vapours is below occupational exposure standards. RPE is critical in most workplaces but we should keep in mind that RPE should only be implemented as a control after attempts at applying the hierarchy of controls have not reduced exposure to acceptable levels.


Different RPE provides different levels of protection, this News article aims to go into more detail around a term called the "protection factor".



What is exactly does the term protection factor mean?


AS/NZS 1715:2009 defines protection factor as “a measure of the degree of protection afforded by the respirator, defined as the ratio of the concentration of contaminant outside the respirator to that inside the respirator”.


Put in layman terms protection factor means that the air inside the respirator is a certain amount cleaner than the air outside the respirator. For example a protection factor of 10 would mean that the air inside the respirator is 10 times cleaner than that of the air outside the respirator.



How do we calculate the protection factor?


To calculate the protection factor we divide the ambient airborne concentration by the concentration inside the respirator.


Without certain equipment this is quite difficult for most business to do- so we simply refer to table 4.2, 4.3 and 4.5 in AS/NZS 1715:2009.  The table states the different protection factors given by different RPE.


Below we look at the protection factors in table 4.2 (for mechanically generated particles), to keep the list short and concise we have only listed common RPE:


Protection Factor of up to 10

  • Use a replaceable P1, P2 or P3 filter in a half face respirator
  • Use a P1 or P2 disposable respirator


Protection Factor of up to 50

  • Use a P2 filter in a full face respirator
  • Use a P3 filter in PAPR with any head covering


Protection Factor of up to 100

  • Use a P3 filter in a full facepiece


Protection Factor of 100+

  • Use P3 PAPR in a full facepiece

The 3M full face RPE with P3 filters gives us a protection factor of up to 100



How do we calculate the required minimum protection factor for RPE being used?


To calculate the required minimum protection factor we divide the ambient airborne concentration by the acceptable exposure level or standard.


As an example consider the following situation:


Task: Working in a quarry digging and excavating quartz for 8 hours per day.


Exposure standard for quartz: 0.1 mg/m³


Worker exposure as a time weighted average: 1.8 mg/m³


Protection factor required= ambient airborne concentration/ acceptable exposure level


Protection factor required= 1.8 / 0.1


Protection factor required= 18


To get a protection factor of 18 we then would refer to table 4.2- to get a protection factor of 18 we could select the following common RPE:

  • P2 filter in full face piece
  • P3 filter in full face piece


As P3 filters used in full face pieces is quite common and gives wearers a higher protection factor we would select this as our RPE.



How we can help?


Pro Safety and Training are experts in AS/NZS1715, respirators, face fit testing, safety training and all things safety.

Topics such a protection factors are a higher level of knowledge and we try implement this higher level of knowledge into all our dealings with public customers and clients, not only to make you aware of this knowledge but so you can learn and develop your workplace around this knowledge.


For more information contact us on 1300 336 003 or email us at [email protected], we can come to you anywhere in Australia or PNG.



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