A hood is placed over the head and a challenge solution is atomised into it while the wearer performs exercises.

If they taste or smell it, the respirator has failed.

Bitter and sweet solutions are the common agents.

The result is a pass or fail rather than a measurement.

It is accepted for disposable and half-mask respirators in most regimes.

That covers the large majority of respirator users.

Confirming the wearer can taste the agent at all before the test begins.

It is done without a respirator, using a dilute solution.

A non-trivial proportion of people cannot detect the agents.

Someone who fails the sensitivity check cannot be tested by this method.

They need quantitative testing instead.

Skipping the sensitivity check makes a subsequent pass meaningless, because a non-detection proves nothing.

Because a respirator that seals while standing still may not seal while working.

The wearer breathes normally and deeply, turns and nods their head, talks and bends over.

Each exercise stresses the seal in a different way.

Talking in particular moves the face considerably.

Skipping exercises to save time invalidates the test.

The specified exercises and their durations come from the applicable method rather than being chosen.

No - the result is specific to a make, model and size.

A pass on one model says nothing about another.

Even a different size of the same model requires its own test.

That is why the record must identify the exact respirator.

Changing supplier or model means retesting everyone affected.

It is a practical argument for standardising on a small number of models.

For full-face respirators in many regimes, and for anyone who fails the sensitivity check.

Full-face respirators provide protection factors higher than a taste-threshold method can demonstrate.

Where the required protection factor exceeds what the method proves, quantitative testing is needed.

Wearers who cannot detect the agent cannot be tested this way.

Which methods are accepted for which respirators is set locally.

Establishing that before setting up a testing programme avoids doing invalid tests.

Hair in the sealing area prevents a seal, and no fit test result changes that.

This applies to tight-fitting respirators of every type.

A day's stubble is enough to compromise the seal measurably.

It is a common source of conflict and needs addressing as policy rather than at the test.

Loose-fitting powered hoods and helmets are the alternative where facial hair cannot be removed.

Testing someone with facial hair in the seal area is not a meaningful exercise.

Someone competent in the method - and competence requirements differ by market.

Some regimes have formal accreditation schemes for fit test operators.

Others require demonstrable competence without a named qualification.

The operator has to conduct the exercises correctly and interpret the result honestly.

Poor technique produces passes that mean nothing.

Records should identify who carried out the test as well as who was tested.