N007
Workplace
Performance Assessment of Activated Charcoal Filters
Robert Rajan-Sithamparanadarajah
Health and Safety Executive,
Magdalen House, Trinity Road,
Tel: +44 151 951 3318 Fax: +44
151 951 3595
e-mail: bob.rajan@hse.gsi.gov.uk
ABSTRACT
Organic vapour filters based on activated charcoal are extensively
used in the workplace for providing protection against substances hazardous to
health present in the air.
Employers
have a duty to select and use these filters correctly. Employers in small and medium sized
enterprises (SMEs), however, do not possess adequate
knowledge and expertise for assessing the effective use time of charcoal
filters. The Health and Safety
Executive (HSE) have found that in a substantial number of cases charcoal
filters have been used for many days or weeks without an assessment being made
to establish the effectiveness of these filters to provide adequate protection
over such long periods. Current HSE guidance in
this area is not helpful to SMEs. HSE consider that further research is needed before
any useful guidance can be formulated.
Adsorption
capacities and lifetimes were measured for CEN Class A1 and A2 filters for a
number of vapours under different conditions such as
air flow rates, vapour concentrations, humidity,
intermittent exposures and mixtures of vapours. HSE tested filters available from a selected number
of manufacturers.
HSE found
that the same class of filter obtained from different manufacturers varied in performance and
the breakthrough times obtained were a cause for concern. A proportion of filters were found to be defective
even though they carried the “CE” marking to indicate that they had been
subjected to quality assurance procedures.
This paper
will present a summary of the data. On the basis of the data, HSE has formulated simple
guidance to SMEs. This guidance does not depend on the use of
predictive models and the user will not be expected to assess the useful
lifetime of filters. In
addition, this guidance will provide a level playing filed for suppliers of the
filters. Where a filter manufacturer
considers that the guidance is too conservative, they are free to provide
guidance to their individual customers.