Labconco 3980200 User Manual - Definition of Terms

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Chapter 5: Using Your Filtered Enclosure and Appropriate Application

THOSE USED AS GUIDELINES FOR THIS 

PRODUCT.  IT IS THE USER’S 

RESPONSIBILITY TO BECOME AWARE OF 

LOCAL REGULATIONS GOVERNING THE 

SAFE USE AND DISPOSAL OF CHEMICALS, 

CARBON AND HEPA FILTERS.  KNOWLEDGE 

OF ESTABLISHED SAFE EXPOSURE LEVELS 

IS IMPERATIVE TO THE PROPER USE OF 

FILTERED ENCLOSURES. 

Definition of Terms 

NIOSH – National Institute for Occupational Safety and 

Health/Mine Safety and Health Administration. (U.S.A.) 

TWA – Recommended Exposure Limits expressed as a Time 

Weighted Average.  The exposure limit for that chemical for up to 

a 10-hour workday, 40 hours a week.  Expressed in units of parts 

per million or milligrams per cubic meter. 

Odor Threshold – The value in parts per million or milligrams per 

cubic meter for which one might expect to smell a chemical’s 

presence in the air.  This value is very subjective and detection will 

vary with the sensitivity of one’s nose.  The period of time until the 

odor threshold is reached in the exhaust stream can be estimated 

from Labconco exclusive computerized filter modeling program.  

Contact Labconco on carbon filter life for specific applications.  

See Chapter 6. 

Saturation Level or Time – There is a limit to the amount of 

chemical that can be adsorbed by activated carbon, or neutralized 

by chemically-treated carbon.  Once the capacity of the carbon is 

reached, it is considered to be saturated and will adsorb (or 

neutralize) no further material; the outlet concentration of the 

chemical will equal the inlet concentration from that point until the 

filter is replaced.  (Note that the capacity of activated carbon is not 

a constant, but varies with the inlet concentration).  Labconco 

Technical specialists can determine with the computerized carbon-

modeling program the estimated time saturation for a particular 

chemical.  When using a HEPA filter alone in all filtered 

enclosures or in combination with an Odor Control carbon filter, 

the speed control will need to be increased to allow for HEPA filter 

loading.  Measure filtered enclosure face velocity with an 

anemometer.