365bet娱乐

Threshold Limit Values (TLVs)

TLVsThreshold Limit Value. A level of concern representing the adverse health effects of a hazardous substance on healthy adult workers. TLVs are not available in CAMEO 365bet娱乐.听补谤别 workplace exposure standards recommended by a committee of the American Conference of Governmental Industrial Hygienists (ACGIH).

What are TLVs?

TLVs are the maximum average airborne concentrationThe amount of a chemical present in a given weight or volume of air. Concentration of a gas in air may be expressed in units such as parts per million (by volume) or milligrams per cubic meter. of a hazardous material to which healthy adult workers can be exposed during an 8-hour workday and 40-hour workweek over a working lifetime鈥攚ithout experiencing significant adverse health effects.

A TLV has three components:

• Time-weighted average (TWA) concentration: The concentration of a contaminant averaged over a workday (usually 8 hours long). It's measured in a workplace by sampling a worker's breathing zone for the whole workday. ACGIH聽recommends that the TWA should not be exceeded for up to an 8-hour workday during a 40-hour workweek.
• Ceiling value: A concentration of a toxicPoisonous; can injure or kill people or other organisms. substance in air that ACGIH recommends should not be exceeded at any time during the workday. This value is often used in conjunction with the TWA.
• Short-term Exposure Limit (STEL) value: A TWA concentration over 15 minutes that ACGIH recommends not to exceed鈥攅ven if the 8-hour TWA is within the standards. TWA-STELs are given for contaminants for which short-term hazards are known.

Below is a graph of concentration over an 8-hour day at a hypothetical workplace. During this day, the TWA and the ceiling value were not exceeded:

• Excursions of concentration above the TWA line were balanced out by periods when concentrations were below the line.
• While the ceiling value was reached, it was never exceeded.

For More Information

• How are TLVs chosen?How are TLVs chosen?

  The American Conference of Governmental Industrial Hygienists committee, with the aid of consultants, meets regularly to update existing TLVs and set new ones. The guidelines are based on available animal and human exposure studies. To find out more about the TLV development process, go to the 听飞别产蝉颈迟别.

• What substances have TLVs?What substances have TLVs?

  TLVs have been recommended for more than 700 hazardous substances. TLVs are published annually in a booklet containing exposure guidelines for many commonly used substances.

• How should TLVs be used?How should TLVs be used?

  It is important to remember that TLVs are recommended values, not legal limits. They do not guarantee protection to all workers and are not intended to be used for public exposure. They are not the fine line between safe and unsafe; rather, TLVs are values that should not be exceeded for long-term exposures (that is, over the course of a working lifetime). The goal is to minimize workers' exposure to hazardous concentrations as much as possible.

TLV Information Online

• 聽Read all about TLVs on this ACGIH site, which contains details about TLV development.
• 聽Lookup chemicals online by name, CAS numberOr CAS #. Chemical Abstracts Service Registry number. This chemical identification number, in the format XXX-XX-X, is assigned by the American Chemical Society (www.cas.org/support/documentation/chemical-substances/faqs)., and UN/NA numberUnited Nations-North American number. (Also UN number or DOT number.) Four-digit number identifying an individual chemical or group of chemicals with similar characteristics. Required on shipping papers; often shown on placards. The four-digit number is often preceded by UN (such as UN1219). on this National Institute of Occupational Safety and Health site to find TLVs for many chemicals.