Time weighted average values

The 1994—1995 threshold limit values as recommended by the American Conference of Governmental Industrial Hygienists (ACGIH) are given in Table 8. These time-weighted average values are those levels to which nearly all workers may be exposed for an 8-h workday and a 40-h work week without adverse effect (99). 

Define what Ceiling, Short term limit, and time weighted average values are. 

Unsteady noise can be evaluated by a phonometer, which measures the sound pressure level for a time period of noise fluctuation and gives the time-weighted average value. 

Note also that C vg = 0.02 ppm, luid (t2-tl) = 15 minutes (tlie range upon which the time-weighted average value is based). 

Standards for individual substances are usually set to reflect ceiling values, a threshold concentration value never to be exceeded even momentarily, and also time-weighted average values,... 

One-hundredth of the concentration that was lethal to 50% of the exposed population [LC50], or one-tenth of the lowest observed lethal concentration [LCLo], for exposure durations of 4 hours, j Threshold limit values or time-weighted average values, for 8-hour ejq)osures. 

Threshold Limit Value/Time Weighted Average value (TLV-TWA) by ACGIH, 2003 5 ppm (equivalent to 21 mg/m ) [4]. 

Time weighted average concentrations (TWA) The limits refer to the maximum exposure concentration when averaged over a 10-minute period or an 8 hour day. The time weighted average value (Cm) may be obtained from the following formula ... 

For considering toxicity manifestation time and vapor dispersion situations in cases of terrorism, it is necessary to initiate the alarm for a vapor concentration of less than the vapor concentration of 1/100 of LCtso within Imin. In the case of GB, the required detection sensitivity is 1.5mg/m at this level, humans show few signs of intoxication, nor is there a detectable odor. In chemical weapon-disposal situations, because workers are present at the sites for a prolonged time, the time-weighted average values, which are approximately 1/100,000 of LCtso, adopted as the monitoring target for allowed operational conditions. An alarm time of less than several minutes is desired. There is a trade-off relationship between LOA, alarm time, detection accuracy. 

Exposure limits (threshold limit value or TLV) are those set by the Occupational Safety and Health Administration and represent conditions to which most workers can be exposed without adverse effects. The TLV value is expressed as a time weighted average airborne concentration over a normal 8-hour workday and 40-hour workweek. 

American Conference of Government Industrial Hygienists (ACGIH) threshold limit value = 5 ppm on an 8-h time-weighted average. 

Threshold limit value, time-weighted average. 

Health and Safety Factors. MEK is slightly more toxic than acetone, but is not considered highly toxic, and nor does it exhibit cumulative toxicological properties. The OSHA time weighted average iu air is 200 ppm other measured toxicity values are shown iu Table 3. Methyl ethyl ketone is highly flammable. 

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. 

Ceiling value concentration which should not be exceeded not appropriate to use a time-weighted average. 

Exposure to tantalum metal dust may cause eye injury and mucous-membrane irritation. The threshold limit value (TLV) in air is 5 mg/m, LD q is <400 mg/kg and the Occupational Safety and Health Administration (OSHA) time weighted average (TWA) exposure limit is 5 mg/m (47). The immediate dangerous to life or health (IDLH) concentration is 2500 mg/m (48). Whereas some skin injuries from tantalum have been reported, systemic industrial poisoning is apparently unknown (47). 

Because pulp bleaching agents are, for the most part, reactive oxidising agents, appropriate precautions must be taken in their handling and use. For example, it is important to ensure that the threshold limit values (TLV) (20) in Table 2 are not exceeded in the workplace air. These are airborne concentrations in either parts per million by volume under standard ambient conditions or mg per cubic meter of air. They "represent conditions under which it is beUeved that nearly all workers may be repeatedly exposed, day after day, without adverse effect" (20). TWA refers to a time-weighted average for an 8-h workday STEL is a short-term exposure limit or maximum allowable concentration to which workers can be continuously exposed for 15 minutes. 

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