Qualitative testing relies on the test subject's ability to smell or taste a contaminant if it leaks into the respirator. It is therefore a subjective test: the test person might have a cold or have a good or poor sense of smell or taste. It is therefore not considered to be very reliable.

Quantitative testing entails using a machine that analyses the air and compares the ambient atmosphere with the atmosphere inside the face piece, thus detecting any leakage by counting contaminant molecules inside the mask.

One common quantitative test machine is known as a PortaCount. The equipment needs to be properly maintained and carefully calibrated according to the manufacturer's instructions. All hoses, tubes and connectors must be thoroughly inspected before each test.

The person doing the testing must be familiar with the test equipment and trained in the proper use of it.

Only tight-fitting face-seal respirators are suitable for standard PortaCount individual fit testing. So-called 'filtering face pieces' are not suitable without extra modules or attachments to the sampling equipment.

Make sure that the respirator size is appropriate for the test person. If the face piece is too big or too small, it will produce negative results.

Use only the filter type recommended in the fit tester instructions. Usually this is high-efficiency particle filters (P3/P100). Other types of filters, such as N95, may be used through special attachments in certain fit testing equipment models.

The respirator and all its parts must be thoroughly inspected before the test. Several factors can adversely influence the test results, including:

Straps	Valves & valve seats	Cracks	Dirty rims
Head straps, bands and harnesses may lose their elasticity over time. They should be taut, elastic and clean. If not, replace before the fit test.	Check both inhalation and exhalation valves for cracks, tears and dirt. Also make sure that the valve seats are clean and smooth to provide perfect seal.	Check the mask body for cracks or other obvious damage.	Dirt on the rim of the face piece may be detrimental to facial seal.

The biggest problem by far in individual fit testing is facial hair. If any hair growth is allowed to interefere with the facial seal, the test will be null and void. This applies to head hair, sideburns, goatees, beards, stubble and even 'five o'clock shadow'.

Other problems may be caused by a variety of facial features, such as:

• acne and other skin conditions
• folds, creases, warts, furrows, wrinkles and other uneven facial features
• missing teeth, dentures, etc.
• unusual facial features, such as large/small/flat/sharp noses and others

After fitting the respirator to the test person, wait a while. The mask will have ambient air inside it, and breathing normally a minute or two with the mask fitted will empty it of contaminants.

QLD: Trevor Heffernan — (0410) 550 123 — trevor@sea.com.au

NSW, New Zealand: Michael Serret — (0411) 470 083 — mick@sea.com.au

VIC, TAS: Stuart Oppawsky — (0410) 606 505 — stuart@sea.com.au

WA, SA, NT: Straff Graso — (0438) 775 531 — straff@sea.com.au