Time-weighted average concentrations

Time-weighted exposure. This is the time-weighted average concentration for a normal 8-hour workday or 40-hour workweek to... 

Phenol fumes are irritating to the eyes, nose, and skin. According to the National Institute for Occupational Safety and Health (NIOSH), exposure to phenol should be controUed so that no employees are exposed to phenol concentrations >20 mg/m, which is a time-weighted average concentration for up to a 10-h work day, 40-h work week. Phenol is very toxic to fish and has a nearly unique property of tainting the taste of fish if present in marine... 

Threshold limit value—time weighted average. Defined as the maximum time weighted average concentration to which a worker may be exposed repeatedly and without adverse effects for a normal 8 h/d, 40 h/wk period. 

The ACGIH recommended maximum time-weighted average concentration in the workplace atmosphere for eight-hour daily exposure is 10 ppm. OSHA has set the permissible exposure level at 2 ppm. It maybe desirable to exclude alcohoHcs, persons with chronic disorders of the Hver, kidneys, and central nervous system, and those with nutritional deficiencies from working with chloroform. 

T T,-STEL is a I5-min, time-weighted average concentration to which workers may be exposed up to four times per day with at least 60 min between successive exposures with no ill effect if the TLV-TWA is not exceeded (developed by the ACGIH). 

TLV-TWA is the time-weighted average concentration hmit for a normal 8-h day and 40-h worlweek, to which nearly all workers may be repeatedly exposed, day after day, without adverse effect (developed by the ACGIH). 

Recommended exposure limit (8 hr time-weighted average concentration) Headache after about 7 hr if resting or after 2 hr exertion... 

LJsually, OELs are stated as the eight-hour time-weighted average concentration of exposure to a substance in gaseous, vaporous, or suspended form in the air at the workplace. Later on we will give a more precise formula. 

Time-weighted average concentration, TWA, based on a 40-hour work week. 

Long-term and short-term limits are expressed as time-weighted average concentrations. For a long-term limit the normal period is eight hours for a short-term limit the normal period is ten minutes. 

Time-weighted average (TWA) TLV - the time-weighted average concentration for a normal 8 hr work day and a 40 hr work week, to which it is believed that nearly all workers may be repeatedly exposed, day after day, without untoward effects. TWA TLVs permit excursions above the TLV provided that they are compensated for by equivalent excursions below the TLV during the work day. The excursion above the TLV is a rule of thumb, as explained in the source reference. 

Recommended exposure limit (8 hr time-weighted average concentration)... 

A direct method for determining worker exposures is by continuously monitoring the air concentrations of toxicants on-line in a work environment. For continuous concentration data C t) the TWA (time-weighted average) concentration is computed using the equation... 

Permissible Exposure Limit (PEL) The maximum time-weighted average concentration mandated by OSHA to which workers may be repeatedly exposed for eight hours a day, forty hours per week without adverse health effects. 

Short Term Exposure Limit (STEL) The time weighted average concentration to which workers can be exposed continuously for a short period of time, normally fifteen minutes, without suffering irritation, chronic or irreversible tissue damage, etc,.. 

An apparatus is used to generate known time-weighted average concentrations of contaminants. The procedure is as follows ... 

Time Weighted Average Concentration Refers to concentrations of contaminants which have been weighted for the time duration of sample. A sufficient number of samples are needed to permit a time-weighted average concentration throughout a complete cycle of operations or throughout the work shift. 

Table 4. Eight-hour time-weighted average concentrations of butadiene to which workers in different jobs in petroleum refineries and petrochemical facilities were exposed from 1984 to 1987...

DNA-protein cross-links caused by formaldehyde, a metabolite from the GST pathway, have been demonstrated in mice but not hamsters exposed to dichloromethane (Casanova et al., 1992). Similarly, in-vitro studies have not demonstrated DNA-protein cross-links in rat, hamster or human hepatocytes exposed to concentrations of dichloromethane of up to 5 mM. This is equivalent to the time-weighted average concentration predicted to occur in mouse liver during a 6-h inhalation exposure to a dichloromethane concentration of > 10 000 ppm [34 700 mg/m ] (Casanova et al., 1997). 

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