Comparison between Qualitative and Quantitative Respirator Fit Testing

Introduction

Sandwell and West Birmingham Hospitals NHS Trust is an integrated care organisation dedicated to improving the lives of local people, maintaining an outstanding reputation for teaching and education, and facilitating innovation and research.

The Trust employs over 7,000 people and spends around £430m of public money, largely drawn from their local Clinical Commissioning Group. That Group and the Sandwell and West Birmingham Hospitals NHS Trust are responsible for the care of 530,000 local people across North-West Birmingham and Sandwell.

Situation

Respirator fit testing is a key component to any respiratory protection programme, protecting staff from airborne hazards. Anyone who wears a tight fitting respirator is required by HSE INDG 479 to perform respirator fit testing. The Infection Prevention and Control Team at the Trust are responsible for providing over 4,000 frontline staff members with respirator fit tests to ensure the FFP3 masks they use are protecting them.

There are two basic types of fit tests: Quantitative Fit Testing (QNFT) and Qualitative Fit Testing (QLFT).

QLFT is a low cost, subjective pass/fail test that exposes the respirator wearer to a chemical stimulant (while donning a test hood) such as Isoamyl Acetate, Sodium Saccharin, Bitrex or Irritant Smoke that can only be detected if the respirator leaks. The respirator wearer must breathe through their mouth, with tongue extended during the fit test to enable detection (tasting) of leakage into the respirator. QLFT methods are often compromised by wellmeaning test operators who skip important steps, unknowingly invalidating the fit test. To properly follow the protocol, a fit test operator must squeeze the nebulizer bulb between 75 and 225 times for each fit test performed. The temptation to get through the test faster is strong, especially when the same test operator fit tests dozens of people per day.

QNFT is an objective test that involves the use of an instrument to measure how well the respirator fits. The measurement is not dependent on the person’s voluntary response. The instrument measures the fit while the person performs a series of special exercises and automatically records the results. An aerosol challenge agent concentration (Cout) is measured outside the respirator and then again inside the respirator (Cin). The ratio of the two measurements (Cout/Cin) is called a fit factor. The minimum fit factor required by HSE, which should be achieved in each of the test exercises when carrying out a quantitative fit test, is 2,000 for a full-face mask, 100 for a half-mask and 100 for FFP3, FFP2 and FFP1 filtering facepieces.

Prior to 2018 at the Sandwell and West Birmingham Hospitals, NHS Trust fit testing was carried out using the Qualitative Hood method. As a result, some staff lost confidence in the accuracy of the system. (...)

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