CLEAN-AIR 02 HOW TO CHOOSE THE RIGHT EQUIPMENT 1. YOU NEED TO KNOW THE CONCENTRATION OF THE HAZARDOUS SUBSTANCE IN A WORKPLACE 2. YOU NEED TO KNOW ASSIGNED WORKPLACE EXPOSURE LIMIT (WEL) The list of the most typical contaminants and relevant WEL´s can be found in our „Filter Guide“ where the information were taken from HSE publication EH40/2005 Workplace Exposure Limits, or you can source it from local authorities. WEL´s are occupational exposure limits (concentrations) of a specific airborne substance averaged over a reference period, to which workers may be exposed without experiencing significant adverse health effects. There are two reference periods for which the WELs may be set: 8-hour Time Weighted Average (TWA) and 15-minute Short Term Exposure Limit (STEL). TWA (TIME WEIGHTED AVERAGE) – 8 HOURS (LONG TERM) TWAs are set to help preventing health effects which require prolonged or accumulated exposure. STEL (SHORT TERM EXPOSURE LIMIT) – 15 MINUTES (SHORT TERM) STELs are set to help prevents health effects which may be seen after short exposure (e.g. eye irritation that could occur after a few minutes) The absence of a substance from the list of WELs does not indicate that it is safe. For these substances, exposure should be controlled to a level to which nearly all the working population could be exposed, day after day at work, without any adverse effects on health. 3. YOU NEED TO DETERMINE THE NEEDED MINIMUM PROTECTION FACTOR OF RPE For example: Powered air purifying respirator incorporating a hood classified as TH3 according to EN 12 941 has a maximum inward leakage of 0,2 %. Therefore NPF = 100 (%) : 0,2 (%)= 500. CONTAMINANT ACETIC ANHYDRIDE (gas protection needed) Concentration at the workplace 100 mg / m3 WEL 2,5 mg / m3 Minimum protection factor = Concentration at the workplace N OMINA L PROT ECT ION FACT O R (NPF) WEL 100 = 40 2,5 Theoretical level of protection of Respiratory Protective Equipment calculated using performance data measured in the laboratory. It indicates the mathematically calculated maximum breathing protection performance. Calculated by dividing 100 by the total value of maximum inward leakage as specified in the relevant standard. DESCRIPTION/ DEVICE CLASS PAPR with TH1 helmet or hood TH2 EN 12941 TH3 PAPR with TM1 half or full face mask TM2 EN 12942 TM3 Continuous flow compressed airline breathing apparatus EN 14594 1A/1B 2A/2B 3A/3B 4A/4B NPF 10 50 500 20 200 2000 10 50 200 2000 ASSIGNED PROTECTION FACTORS (USED IN SOME COUNTRIES) FIN D I S UK 5 5 5 5 5 20 20 20 20 20 200 100 200 200 40 10 10 10 10 10 100 100 100 100 20 1000 500 400 1000 40 - - - - - - - - - - - - - - - - - - - - WHAT IS THE MAXIMUM CONCENTRATION OF THE CONTAMINANT FOR WHICH I CAN USE RESPIRATORY PROTECTION? You can determine the maximum permissible concentration by multiplying the nominal protection factor (as found in the NPF table) by the Workplace Exposure Limit. CAUTION! In the case where the contaminants are present in both particle and gas form, the neccessary NPF must be established for each one separately and the higher protection factor must be applied.
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