Do we really need to fit test FFP respirators?

The purpose of a fit test is to ensure that each and every wearer uses a facepiece (FFP, halfmask or full facemask) which can seal well to their face. Fit testing has been included in Health and Safety Executive (HSE) Approved Codes of Practice for several years, but it requires a trained competent person to carry it out, takes time and therefore incurs some cost.  Is fit testing really necessary? Where disposable filtering facepieces are concerned, could a wearer fit-check be sufficient? 

Many RPE manufacturers include in their instructions advice to fit-check the facepiece after putting it on.  Manufacturers advise fit-checking as a guide to ensuring that the facepiece has been correctly put on. For FFP the instruction usually given for fit-checking involves the wearer trying to block air getting in or out of the facepiece, by loosely covering the filtering material with their hands, and breathing in or out sharply being alert for any air leaking around the edges of the facepiece. 

Are fit-checks a suitable method for detecting poor fit of FFP? 

A recent study by scientists at HSL has shown that there is very little value in fit-checking as a substitute for a fit test, where filtering facepieces class 3 (FFP3) are concerned:

fit-checking correctly detected only 18% of poor fitting FFP3 

fit tests correctly detected at least 88% of poor fits – Bitrex (qualitative taste test) and Portacount (particle counting) fit test methods 

The Bitrex and Portacount fit tests are in common use for fit testing FFP3 and discussed in HSE guidance1. Results were measured against the laboratory test chamber fit test method1 often considered to be the most reliable reference method, derived from the European Standard total inward leakage test. The fit-check results closely match those from a similar study carried out in Hong Kong2.

HSL’s study also showed that more often than not FFP3 do not adequately fit the wearer if selected at random, therefore the need for fit testing becomes even more necessary. 

HSL compared the outcomes of different fit test methods when applied to nine models of FFP3. Volunteer test subjects were asked to put on an FFP3 and take part in four different fit test methods (Bitrex, Portacount, Portacount-with-N95-companion, Laboratory test chamber), without disturbing the fit until the test run (all four fit tests) had been completed. 

 

All fit test runs were preceded with a fit-check by the wearer and a subjective assessment of the fit (aided by head movements as used in a fit test) by both the wearer (alert for leaks, facepiece movement or insecurity) and the fit tester (visual assessment). Following the fit tests, the wearer and the fit tester again both made a subjective assessment of the fit. Fit tests were carried out by BSIF Fit2Fit accredited3 fit testers.

The reality was that the fit-checking and the subjective assessment alone could lead the wearer to a false sense of security that the fit was good. Sixty one test runs resulted in a fail in all four fit test methods, but over 70% of these 61 poor fits were not assessed as poor by the wearer before the test run began. Even after wearing the FFP3 for an hour whilst four different fit tests were carried out, 25% of wearers still thought that the fit was good. Similarly for 38% of these 61 poor fits, the experienced Fit2Fit accredited fit testers also subjectively assessed that the fit was good, again even after the four fit tests had been completed. 

With all classes of FFP being of similar design and construction to FFP3 it is best to assume that fit testing is needed for demonstrating suitability for all FFP. This work does demonstrate that fit-checking should not be used as a substitute for the robustness of a fit test, however the value of fit-checking as recommended by FFP manufacturers as an aid to correct donning of fit tested FFPs is not being questioned. 

HSE Guidance: Fit testing of Respiratory Protective Equipment Facepieces HSE OC 282/28 (30/4/2012) www.hse.gov.uk/foi/internalops/fod/oc/200-299/282_28.pdf

Lam et al; (2011) Sensitivity and specificity of the user -seal -check in determining the fit of N95 respirators; Journal of Hospital Infection Vol 77, Issue 3, March 2011, pages 252-256 Proceedings from the Sporicidal Workshop

www.fit2fit.org/

 

‘This publication describes work funded by the Health and Safety Executive (HSE).  Its contents, including any opinions and/or conclusions expressed, are those of the authors alone and do not necessarily reflect HSE policy.’

Shirley Frost is a higher scientist in the PPE team at the Health and Safety Laboratory.