Threshold limit value definition

Maximum allowable concentration (MAC) An old American definition used before the term TLV came into use (the term is still used in Germany). See Threshold limit value (TLV). 

Table 2-7 Definitions for Threshold Limit Values (TLVs)1...

TLV The TLV or Threshold Limit Value refers to a safe level of exposure by inhalation. The definition was established by the American Conference of Governmental Hygienists. There are several variations or criteria levels for the TLV. As an example, hydrogen sulfide has a TLV for short-term exposure limits (STEL) of 15 minutes of only 5 ppm. Comparing this to the TLV-STEL of 400 ppm for carbon monoxide provides an indication of the need to be extremely careful when H2S is suspected. Under OSHA Standards, and particularly on MSDS (Material Safety Data Sheets) compounds are associated with a time weighted average (TWA) TLV, which is the allowable concentration for an 8-hour continuous exposure period. For firefighting purposes, the short-term exposure is likely more realistic. 

MAK values can be best compared, at an international level, with the definition of the Threshold Limit Values (TLV) of the American Conference of Governmental Industrial Hygienists, which may be expressed as a time-weighted average (TWA), as a short-term exposure (STEL), or as a ceiling value (CL).8... 

The threshold limiting value of respiratory exposure is 1 mg/cm of air. In the (breathable) atmosphere,. .. 0.125 to 0.50ppm may be mildly annoying and 1.5 to 2.5ppm can be definitely unpleasant 10 to 20ppm is unbearable. . . Body contact results in rapid de-... 

Environmental criteria have been established for many of these, but the utility and applicability of such criteria for indoor environments is controversial for at least four reasons. Eor example, the goals of the threshold limit values often do not include preventing irritation, a primary concern in indoor environments with requirements for close eye work at video display terminals. For most of the pollutant categories, the problem of interactions, commonly termed the multiple contaminants problem , remains inadequately defined. Even for agents that are thought to affect the same receptor, such as aldehydes, alcohols, and ketones, no prediction models are well established. Finally, the definition of representative compounds for measurement is unclear. That is, pollutants must be measurable, but complex mixtures vary in their composition. It is unclear whether the chronic residual odor annoyance from environmental tobacco smoke correlates better with nicotine, particulates, carbon monoxide, or other pollutants. The measure total volatile organic compounds is meanwhile... 

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 Value - The term refers to toxicity by inhalation Hie abbreviation used is TLV. The ILV is usually expressed in units of parts per million (ppm) - i.e., the parts of vapor (gas) per million parts of contaminated air by volume at 2S °C (77 °F) and atmospheric pressure. For chemicals that form a fine mist or dust, the concentration is given in milligrams per cubic meter (mg/m. The TLV is defined as the concentration of the chemical in air that can be breathed for five consecutive eight-hour workdays (i.e., 40 hours per week) by most people without suffering adverse health effects. This is the definition given by the American Conference of (jovemmental Industrial Hygienists. 

The TLV is one of various indices of permissible exposure levels to chemicals another is the Short Term Exposure Limit (STEL), which represents a 15-minute concentration which should not be exceeded in an 8-hour workday. Its aim is particularly to prevent the acute effects of short-term exposure. STEL values can be found, along with a more precise definition, in Threshold Limit Values, published by the ACGIH (Cincinnati, USA). 

CAS No. is the Chemical Abstracts Service Registry Number PEL is from 29 CFR 1910.1000, Table Z-1 American Conference on Governmental Industrial Hygienists (ACGIH), threshold limit value (TLV) under the HCS, a MSDS is required for aU of the compounds (physical and/or chemical hazard) all of the solvents are flammable liquids or gasses, under the OSHA definition, and are regulated under the PSM Standard. 

The material is definitely proved to be carcinogenic for this reason, no Threshold Limit Value is given. 

TLV The TLV or Threshold Limit Value refers to a safe level of exposure by inhalation. The definition was established by the American Conference of Governmental Hygienists. There are several variations or criteria levels for the TLV. As an example, hydrogen sulfide has a TLV for s t 0... 

The threshold of sensitivity varies according to the instrument and the element being considered. Numerous comparative tables on detection limit values exist which are continually being updated as a result of the progress made in instrumentation. The sensitivity threshold corresponds to the minimum concentration of element in solution that will yield an analytical signal for which the amplitude is equal to three times the standard deviation calculated for an analytical blank. This classic definition leads to rather optimistic values and very variable with respect to the element. The detection limit of the instrument represents the concentration of an element, which allows detection with a confidence of 95 per cent (cf. Chapter 22). 

Performance is defined by the sensitivity threshold, or the minimum concentration of element in solution that will yield an analytical signal with amplitude equal to twice that of the average background signal. This classical definition leads to optimistic values that can vary from element to element. The limit of detection represents the concentration of an element that can be detected with a 95% confidence limit (cf. chapter 21). In general, measurements are made in a concentration domain that corresponds to 50 times the limit of detection. 

We shall consider two extreme kinds of systems. In the first kind, the system is a conductor and by application of a voltage between two electrodes (for the sake of simplicity the two electrodes will be taken parallel) a current flows from one electrode to another. The failure occurs when the current density becomes larger than a threshold value. Consequently, the system becomes nonconducting. The system behaves exactly as a fuse which is destroyed when the current is too large. We shall call this failure the fuse failure. In the second case, the system is a perfect insulator and a voltage is applied between the two electrodes. Again, beyond a definite (threshold) value of the electric field, the system breaks down and becomes conducting. This phenomenon is well-known in the physics of dielectrics, since it limits the application of dielectrics as insulators. We shall talk about the dielectric problem for this kind of failure. 

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