TLV-TWA

Current TLV/TWA values are provided in Matena/Safety Data Sheets provided by manufacturers upon request. Values for 1989 (83,107) appear in Table 5. 

Exposure limits for siHcon carbide and powders of zirconium compounds (including zirconium dioxide) have been estabHshed by ACGIH. TLV—TWA s are 10 mg/m and 5 mg/m, respectively. OSHA guidelines for zirconium compounds call for a PEL of 5 mg/m. There are no exposure limits for siHcon nitride powder, but pmdent practice suggests a TLV—TWA of 0.1 mg/m. The soHd ceramics present no apparent health hazard. In machining such ceramics, however, care should be taken to prevent inhalation of respirable particles in amounts in excess of estabHshed limits. Disposal should be in approved landfills the materials are inert and should pose no danger to the environment. 

The OSHA permissible exposure limit (11) and the American Conference of Governmental Industrial Hygienists (ACGIH) estabHshed threshold limit value (TLV) (12) for fluorides is 2.5 mg of fluoride per cubic meter of air. This is the TLV—TWA concentration for a normal 8-h work day and a 40-h work week. 

The ACGIH adopted TLV/TWA for 1992—1993 for fluorides as F is TWA 2.5 mg/m, and for cobalt as Co metal dust TWA 0.05 mg/m. Dust masks should be used while handling both the cobalt fluorides and all other cobalt compounds. CoF is shipped as an oxidizer and a corrosive material. 

Exposure to formic acid vapor causes irritation of the eyes and respiratory tract. The TLV/TWA occupational exposure limit is 5 ppm (40). Self-contained breathing apparatus should be used when there is a risk of exposure to high vapor concentrations. 

The U.S. Occupational Safety and Health Administration (OSHA) has set a ceiling level for iodine of 0.1 ppm in air. The American Conference of Government and Industrial Hygienists (ACGIH) estabUshed 0.1 ppm as the TLV (TWA) for iodine. The maximum allowable concentration in air (MAK value) is also 0.1 ppm (104—106). 

The threshold limit value—time integrated average, TLV—TWA, of chlorine dioxide is 0.1 ppm, and the threshold limit value—short-term exposure limit, STEL, is 0.3 ppm or 0.9 mg /m of air concentration (87,88). Chlorine dioxide is a severe respiratory and eye irritant. Symptoms of exposure by inhalation include eye and throat irritation, headache, nausea, nasal discharge, coughing, wheezing, bronchitis, and delayed onset of pulmonary edema. Delayed deaths occurred in animals after exposure to 150—200 ppm for less than one hour. Rats repeatedly exposed to 10 ppm died after 10 to 13 days of exposure. Exposure of a worker to 19 ppm for an unspecified time was fatal. The ingested systemic effects of low concentration chlorine dioxide solutions are similar to that of chlorite. 

Safety. Chlorosulfuric acid is a strong acid and the principal ha2ard is severe chemical bums when the acid comes into contact with body tissue. The vapor is also ha2ardous and extremely irritating to the skin, eyes, nose, and respiratory tract. Exposure limits for chlorosulfuric acid have not been estabhshed by OSHA or ACGIH. However, chlorosulfuric acid fumes react readily with moisture in the air to form hydrochloric and sulfuric acid mists, which do have estabhshed limits. The OSHA 8-h TWA limits and ACGIH TLV—TWA limits are sulfuric acid = 1 mg/m hydrochloric acid = 5 ppm or 7 mg/m (ceiling limit). 

Measures of inhalation toxicity include ERPG, TLV, TLV-STEL, TLV-TWA, PEL, and IDLH. 

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). 

TLV-TWA, THRESHOLD LIMIT VALUE - TIME WEIGHTED AVERAGE (USa) A limit fOf the atmOSpliei ic concentration of a chemical, averaged over an 8-hr day, to which it is believed that most people can be exposed without harm. 

Talc (containing no asbestos fibres) Talc (containing asbestos fibres) 1 2 (respirable du Use asbestos TLV-TWA... 

TLV-TWA Threshold Limit Vahie-Time-Weighted Average... 

TLV-TWA is defined as the time-weighted average concentration for a normal 8-hour workday and a 40-hour workweek, to wliich nemly all workers may be repeatedly c.xposcd, dtiy after day, witliout any long-tenii adverse effect. 

Class A signifies refrigerants for which toxicity has not been identified at concentrations less than or equal to 400 ppm, based on data used to determine Threshold Limit Value-Time Weighted Average (TLV-TWA) or consistent indices from Section 6.1.2. ... 

With regard to limiting the concentration of particular contaminants, these are generally referred to in terms of threshold limit values (TLV), expressed either in terms of a time-weighted average (TLV - TWA) which represents the average concentration for a normal working day over a 40-hour week to which nearly all workers may be exposed on a repeated basis or as a short-term exposure limit (TLV - STEL), which represents the maximum... 

Short-Term Exposure Limit (STEL)—The American Conference of Governmental Industrial Hygienists (ACGIH) maximum concentration to which workers can be exposed for up to 15 min continually. No more than four excursions are allowed per day, and there must be at least 60 min between exposure periods. The daily Threshold Limit Value - Time Weighted Average (TLV-TWA) may not be exceeded. 

The value is for dust containing <5% silica. For dust containing more than this percentage of free silica, the environment should be evaluated against the TLV-TWA of 0.1 mg/m for respirable quartz. 

TLV-TWA Threshold Limit Values - Time Weighted Average in Vapour... 

TLV-TWA, THRESHOLD LIMIT VALUE - TIME WEIGHTED AVERAGE (USA) A limit for the atmOSpheriC... 

There are three biological exposure indices (BEls) for exposure to trichloroethylene at the ACGIH threshold limit value time-weighted average (TLV-TWA) of 50 ppm (ACGIH 1996). When measured at the end of a 40-hour workweek, TCA in urine is approximately 100 mg/g creatinine when measured at the end of an 8-hour shift at the end of a workweek TCA and trichloroethanol in urine is approximately 300 mg/g creatinine, and free trichloroethanol in blood is approximately 4 mg/L. 

TR Transport Code risk degree for dangerous materials TWA Abbreviation for TLV/TWA (Threshold limit value/Time weighted)... 

Finally, STEL (short term exposure limit) corresponding to the definition of LVE and TLV/TWA (direshold limit value/time weight average) are the equivalent of the French MVE. There are sometimes differences in values between STEL and LVE on the one hand, and TWA and MVE on the other hand. 

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