Airborne concentrations threshold limits

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. 

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. 

Threshold limit value (TLV) The limits of airborne concentration of chemical substances that are allowed in workplaces published by the American Conference of Governmental and Industrial Hygienists (ACGIH). Also known as MAC. 

Threshold Limit Value (TLV) The airborne concentration of a potentially toxic substance to which it is believed healthy w orking adults may be e.xposed... 

Threshold Limit Value TEV) Maximum values of concentrations of airborne toxic contaminants, listed by the American Conference of Governmental Industrial Hygienists (ACGIH), regarded to be safe for 8 hours per day exposure. 

Filter samples can be prepared to airborne workplace concentrations by spiking each filter with aqueous solution containing elements with concentrations gravimetrically traceable to ultrapure metals or stoidiiometricaUy well defined oxides. The amormts correspond for some of the materials to current threshold limit values of contaminants in workroom atmospheres provided that the simulated filter has been exposed to one cubic meter of air. The certified values are based on a gravimetric procedure, i.e. weight per volume composition of the primary reference material dissolved in high purity sub-dis-tiUed acids. The National Institute of Occupational Health in Oslo, Norway, has produced several batches of such materials certified for 20 elements. Additionally, information values are reported for four other elements see Table 6.2. 

Threshold Limit Value Airborne concentrations of substances devised by the ACGIH that represent conditions under which it is believed that nearly all workers maybe exposed day after day with no adverse effect. TLV s are advisory exposure guidelines, not legal standards, based on evidence from industrial experience, animal studies, or human studies when they exist. There are three different types of TLV s Time Weighted Average (TLV-TWA) Short Term Exposure Limit (TLV-STEL) and Ceiling (TLV-C). (See also PEL)... 

TLV Threshold Limit Value. An estimate of the average safe airborne concentration of a substance conditions under which it is believed that nearly all workers may be repeatedly exposed day after day without adverse effect. 

Threshold limit values (TLVs) refer to airborne concentrations of substances and represent conditions under which it is believed that nearly all workers may be repeatedly exposed day after day without adverse effect. Because of wide variation in individual susceptibility, a small percentage of workers may experience discomfort from some substances at or below the threshold limit a smaller percentage may be affected more seriously by aggravation of a preexisting condition or by development of an occupational illness. Threshold limits are based on the best available information from industrial experience, from experimental human and animal studies, and when possible, from a combination of the three. The basis on which the values are established may differ from substance to substance protection against impairment of health may be a guiding factor for some, whereas reasonable freedom from irritation, narcosis, nuisance, or other forms of stress may form the basis for others. Three categories of TLVs follow ... 

Threshold limit value (TLV) The concentration of an airborne substance to which an average person can be repeatedly exposed without adverse effects. TLVs may be expressed in three ways 1) TLV-TWA (Time weighted average), based on an allowable exposure averaged over a normal 8-hour workday or 40-hour workweek 2) TLV-STEL (Short-term exposure limit) or maximum concentration for a brief specified period of time, depending on a specific chemical (TWA must still be met) and 3) TLV-C (Ceiling Exposure Limit) or maximum exposure concentration not to be exceeded under any circumstances. TWA must still be met. 

PEL (Permissible Exposure Limit) or TLV-TWA (Threshold Limit Value-Time Weighted Average). This is the maximum permitted concentration of the airborne chemical in volume parts per million (ppm) for a worker exposed 8 hours daily. 

Exposure Limits PELs and TLVs. Threshold limit values (TLVs) were developed in the 1940s, long before the existence of OSHA. The TLV is defined as the airborne concentration of a contaminant to which it is believed that most workers may be repeatedly exposed, day after day, without developing adverse health effects. Developed and maintained by the American Conference of Governmental Industrial Hygienists (ACGIH), these values have been determined based on industrial experience and animal and human studies. 

Hence, organic solvents should be handled with care. In the USA, the threshold limit values [TL values) are used as a measure of the inhalation toxicity for chronic interaction with solvent vapours [90]. In the Federal Republic of Germany, the maximum concentration values at the workplace [MAK values) are used [91, 92]. Threshold limit values refer to airborne concentrations of substances and represent conditions under which it is believed that workers may be repeatedly exposed daily without adverse effect. They refer to time-weighted average concentrations for a normal 8-hour workday... 

Employees are frequently monitored when working in an environment where exposure to toxic metals is a possibility. The most common form of monitoring involves quantification of airborne concentrations of metals in the production process. Threshold limit values for airborne concentrations and time-interval exposure concentrations are defined by the U.S. National Institute for Occupational Safety and Health (NIOSH) to ensure worker safety. Workers may also be monitored by quantification of biological samples. The most common sample used is a random urine sample, and results are expressed in concentration units for the metal of interest per gram of creatinine to normalize for... 

Threshold Limit Value. (TLV). A set of standards established by the American Conference of Governmental Industrial Hygienists for concentrations of airborne substances in workroom air. They are time-weighted averages based on conditions that it is believed that workers may be repeatedly exposed to day after day without adverse effects. The TLV values are revised annually and provide the basis for the safety regulations of OSHA. They are intended to serve as guides in control of health hazards rather than definitive marks between safe and dangerous concentration. In this book, these are indicated by TLV. 

Threshold limit for allowable airborne concentration in parts per million by volume at 25 °C and atmospheric pressure... 

Several organizations recommend limits of exposure to airborne contaminants in the workplace. These include the Occupational Safety and Health Administration (OSHA), the National Institute for Occupational Safety and Health (NIOSH), and the non-governmental organization, American Conference of Governmental Industrial Hygienists (ACGIH). The threshold limit value (TLV) for a substance is defined as the concentration level under which the majority of workers may be repeatedly exposed, day after day, without adverse effects. The TLV recommendations are given in two forms ... 

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