Labconco 3940200 User Manual - Determination of When to

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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