SELECTING AND USING FILTERS
1. Fully identify the prevailing workplace hazards, checking the scientific names of the chemicals. Ensure that the state of the substance is known, is it a gas, vapour or particle, or indeed a mixture of these.
Special attention is needed if there are several substances that may interact, either by reacting chemically, or by having synergistic adverse health effects.
2. Check the filter type in the following table.
3. Estimate the likely atmospheric concentration. This is best done by measurement, and where this is possible, it is strongly recommended that a workplace survey is carried out. This is particularly important if the substance has long term health effects e.g. carcinogens, respiratory sensitizers, toxic metals.
Where measurement is not possible, an estimate should be made of the maximum likely concentration.
I. Choose a particle filter.
II. Ensure that it has the correct efficiency for the application and that it is correctly marked for the respirator (powered systems).
III. Ensure that the filter is new and undamaged. Check that it is suitable for liquid / mists / bacteria / virus / metal fume, as applicable.
IV. Mark date and time of first use on the filter label or record separately if this is not convenient.
V. Replace the filter when breathing resistance becomes noticeable higher or when a powered respirator fails the flow test.
VI. If the filter has been used against toxic dusts, bacteria or virus, it is usual to dispose of it as contralled waste after each use.
VII. Always replace a particulate filter after 6 months of use regardless of any of the above.
(i) Choose the correct filter type (see table).
(ii) Ensure that it is new and undamaged and not time expired.
(iii) Mark date and time of first use on the filter
(iv) Check duration with the manufacturer.
(v) Replace filters when calculated duration
(vi) If the duration is not known, extreme caution should be exercised when using filters.
(vii) If the substance is tasted or smelt, the filter must be replaced immediately.
(viii) If the substance has poor warning properties (taste/smell) and the concentration is not known, then gas filters should not be used. Consider air supplied equipment.
(ix) Do not use a gas filter which has been out of its packaging for more than six months regardless of any of the above.
The above requirements should be read together for applications which require combination filters.
