Evaluation of the operator protection factors offered by positive pressure air suits against airborne microbiological challenge

Abstract

Laboratories throughout the world that perform work with Risk Group 4 Pathogens generally adopt one of two approaches within BSL-4 environments: either the use of positive pressure air-fed suits or using Class III microbiological safety cabinets and isolators for animal work. Within the UK at present, all laboratories working with Risk Group 4 agents adopt the use of Class III microbiological safety cabinet lines and isolators. Operator protection factors for the use of microbiological safety cabinets and isolators are available however; there is limited published data on the operator protection factors afforded by the use of positive pressure suits. This study evaluated the operator protection factors provided by positive pressure air suits against a realistic airborne microbiological challenge. The suits were tested, both intact and with their integrity compromised, on an animated mannequin within a stainless steel exposure chamber. The suits gave operator protection in all tests with an intact suit and with a cut in the leg. When compromised by a cut in the glove, a very small ingress of the challenge was seen as far as the wrist. This is likely to be due to the low airflow in the gloves of the suit. In all cases no microbiological penetration of the respiratory tract was observed. These data provide evidence on which to base safety protocols for use of positive pressure suits within high containment laboratories.

Keywords: OPF; Risk Group 4; aerosol microbiological challenge; positive pressure suits.

Figure 1

(a,b) Animated mannequin within the stainless steel exposure chamber. (c) Front view of mannequin dressed in surgical scrubs and the Respirex Simplair suit. (d) Rear view of suited mannequin showing fans within the exposure chamber. The red coiled pipe is the supply air and the white pipe is the breathing air supply. (e) Close-up view of the breathing air supply pipe with GF/A filter.

Figure 2

Sampling positions on mannequin.

Figure 3

An example of the cut made in the glove of suits 3 and 4.

Figure 4

A cut in the inner thigh area of the leg of suit 5.