Time-weighted average formula

Health and Safety. Remover formulas that are nonflammable may be used in any area that provides adequate ventilation. Most manufacturers recommend a use environment of 50—100 parts per million (ppm) time weighted average (TWA). The environment can be monitored with passive detection badges or by active air sampling and charcoal absorption tube analysis. The vapor of methylene chloride produces hydrogen chloride and phosgene gas when burned. Methylene chloride-type removers should not be used in the presence of an open flame or other heat sources such as kerosene heaters (8). 

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. 

Worker exposure to alkanes, especially the lower-molecular-mass compounds, is most likely to come from inhalation. In an effort to set reasonable values for the exposure by inhalation of vapors of solvents, hydrocarbons, and other volatile organic liquids, the American Conference of Governmental Industrial Hygienists sets threshold limit values (TLVs) for airborne toxicants.1 2 The time-weighted average exposure (E) is calculated by the formula... 

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 ... 

If an employee is exposed to lead for more than 8 hours in any work day the employees allowable exposure, as a time weighted average (TWA) for that day, shall be reduced according to the following formula ... 

Time-weighted average exposures for an 8-hour work shift are calculated by the following formula. 

Name Comments Formula CAS Reg. No. Time-weighted average exposure limit... 

The permissible exposure limit (PEL) is 2 mg/m for respirable coal mine dust, which is measured gravimetrically as an 8-hour time-weighted average (TWA) concentration. This Hmitis reduced when the respirable silica (quartz) content exceeds 5%. A formula of 10 divided by the percentage of respirable silica is used to determine the reduced PEL for respirable coal mine dust. For example, a sample with 10 pet silica would have a dust PEL of 1 mg/m3 (Code of Federal Regulations, 30 CFR 70.101 and 71.101). For the 10-year period from 1987 to 1996, 7.4% of coal mine inspector samples exceeded the PEL. 

Chain transfer occurs frequently during the polymerization of vinyl chloride. The ratio of propagation events to chain transfer events in a given time period determines the average molecular weight of the final polymer. This finding can be summarized by the empirical formula ... 

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