Chapter 6: Maintaining Your Filtered Enclosure
Determination of When to
Replace Odor Control Carbon
Filters and How to Replace
The carbon filters MUST be replaced when any one of the following two conditions are met:
1.The filtered enclosure outlet (exhaust) concentration approaches the inlet concentration, indicating filter saturation.
2.The odor in the work area becomes intolerable or the concentration of the chemical in the work area is greater than the TWA.
There are four means of determining when its time to change the carbon filters (not shown in the order of preference).
Odor - A person’s sensitivity to odor, tolerance of odor and their comfort level under odoriferous conditions vary with the individual. While odor is an indicator that chemicals are passing through the carbon filter, several points need to be understood:
•Odor within the room is not necessarily an indication of saturation or hazardous exposure concentrations.
•Odor can be used as a prompt to sample the chemical concentration on the exit side of the carbon filter.
•Organic chemicals approved for use in the filtered enclosure have odors that are detectable before reaching the time weighted exposure limits.
Detection Tubes - Color change indicators can be used to measure the concentration of the chemical at the exit side of the carbon filter or in the outlet exhaust. A kit including syringe pump and flexible tubing can be purchased as an accessory from Labconco (Catalog # 6924900). Labconco Customer Service Representatives are supplied with detector tube catalog numbers, as well as telephone numbers to direct you to where to purchase these items.
For Organic, Formaldehyde and Ammonia, chemical specific detector tubes should be purchased when installing fresh filters. Each kit contains instructions on how many strokes of the syringe are required to obtain the stated sensitivity. The sampling syringe is connected to the filtered enclosure exhaust. Connect the syringe to the detector tube while the system is running and pull the air through the tube with the syringe. Each stroke of the
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