Replacement of filters

Theory

Filter Media Types

A typical GC/MS laboratory gas filter system contains three types of filtering media:

• Oxygen Catalyst for absorbing traces of oxygen
• Activated Carbon for adsorbing hydrocarbons
• Molecular Sieve for adsorbing moisture

These filter media types can be divided into two groups:

Chemically absorbent media is like a Venus fly trap, when it comes in contact with a contaminate it absorbs it and does not let it go. Adsorption differs from absorption, which also removes thiings, but the result is swelling of the media. The media size increase equals the amount of material removed.
Surface adsorbent media is like a floor mop, where the contaminant is trapped onto the surface of th media and retained. The material doing the adsorption does not change in size.

Filter Media Breakthrough indicators

The visual indicators are mainly for urgent situations such as a leak or high amount of impurities breaking through. Indicators are typically placed behind the filter media bed. When they change colour shortly after installation of the filter it usually means there is a leak or that the gas distribution system including the manifold to which the filter is connected was not flushed properly prior to - or during - installation of the filter.

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