Permissible exposure limit defined

Short Term Exposure Limits - Defined as the parts of vapor (gas) per million parts of contaminated air by volume at 25 C (77 °F) and atmospheric pressure. The limits are given in milligrams per cubic meter for chemicals that can form a fine mist or dust. The values are the maximum permissible average exposures for the time periods specified. The term Short Term Exposure Limit, or STEL, is also used and is considered interchangeable with Short Term Inhalation Limit. The STEL designation is derived from the OSHA standards. 

OSHA PEL-TWA (Occupational Health and Safety Administration, Permissible Exposure Limits - Time Weighted Average) (NIOSH, 2005) is defined analogous to the ACGIH-TLV-TWA, but is for exposures of no more than 10 h/day, 40 h/week. 

The US Congress passed the Occupational Safety and Health Act in 1970. This act created the Occupational Safety and Health Administration (OSHA) in the federal Department of Labor to establish and enforce safety standards for the workplace. OSHA standards are called permissible exposure limits (PELs). Many PELs have been adopted from ACGIH TLVs. TLVs are generally defined as air concentrations of chemicals that most workers can be exposed to for an 8 h workday, 40 h week for a working lifetime without suffering adverse effects. TLVs are not guaranteed as safe exposure levels for the entire population. Employers may also institute voluntary exposure limits either because an OSHA standard has not been promulgated for a xenobiotic of concern or because they want to apply an exposure limit that is more protective than either the PEL or the TLV. 

OSHA uses the term Permissible Exposure Limit (PEL) to define the maximum concentration of a listed contaminant to which an unprotected worker may be exposed. 

To understand the proper level of respiratory protection, you must conduct a hazard assessment to define your potential workplace exposures. This assessment will define if the hazards are Immediately Dangerous to Life and Health (IDLH) or non-IDLH. This is critical information needed to define whether an air-purifying respirator (APR) is suitable or if an air supplied respirator is required. The National Institute for Occupational Safety and Health (NIOSH) Pocket Guide to Chemical Hazards (www.cdc. gov/niosh/npg/) is a comprehensive resource that will define IDLH levels for most hazards you will encounter. The Pocket Guide will also define specific characteristics of your hazard of concern as well as provide the NIOSH Recommended Exposure Limit (REL) and OSHA Permissible Exposure Limit (PEL). 

Hearing loss is presumed to be work-related if the employee is exposed to noise in the workplace at an 8-hour time-weighted average of 85 dBA or greater, or to a total noise dose of 50 percent, as defined in OSHA s Occupational Noise Exposure standard. Noise dose is defined as the amount of actual employee exposure to noise relative to the permissible exposure limit for noise. A dose greater than 100 percent represents exposure above the limit. For hearing loss cases where the employee is not exposed to this level of noise, refer to the rules in 1904.5 to determine if the hearing loss is work-related. 

Similarly, the Revisions to UFC Article 80 required that a continuous gas-detection system shall be provided to detect the presence of gas at or below the permissible exposure limit or ceiling limit. The detection system shall initiate a local alarm and transmit a signal to a constantly attended control station. The alarm shall be both visual and audible and shall be designed to provide warning both inside and outside of the storage area. The audible alarm shall be distinct from all other alarms. It defined a continuous gas detection system as a gas-detection system where the analytical instrument is maintained in continuous operation and sampling is performed without interruption. Analysis may be performed on a cyclical basis at a frequency not to exceed 30 minutes. P1... 

Specific concentration limit refers to a critical gas concentration limit that should not be exceeded. This limit can be a Threshold Limit Value (TLV), Time Weighted Average (TWA), Permissible Exposure Limit (PEL), Short Term Exposure Limit (STEL), Lower Explosive Limit (LEL) or Immediate Danger to Life and Health (IDLH) limit. These limits can be defined in terms of percent volume (%), parts per million (PPM), or even parts per billion (PPB) Table 1 lists hazards and exposure limits for several common hazardous gases foimd in the electronics industry. Critical gas concentration limits may be mandated by environmental, health and safety statutes, regional or local codes, local code enforcement officials, internal risk management personnel, or an established organizational policy. 

Several organizations recommend limits of exposure to airborne contaminants in the workplace. These include the Occupation 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 (also known as permissible exposure limit, PEL) 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 ... 

Permissible exposure limit (PEL) (safety) Permissible exposure limits to hazardous materials (defined by the OSHA). See also Short-term exposure limit (STEL) Time-weighted average (TWA). 

In 1955, the International Commission on Radiological Protection set a maximum permissible occupational concentration of 3.7 x 103 Bq m-3 (10-10 Ci l-1), for continuous exposure, equivalent to 1.1 x 104 Bq m-3 (3 x 10-10 pCi P1) for a 40-h working week. Subsequently, when it was realised that the critical dose to the lung was from inhalation of decay products, not radon itself, the permissible concentration was defined in terms of the concentration of decay products. The current recommended limit (ICRP, 1986) for a working period of 2000 h per year is 1.5 x 103 Bq m 3 equilibrium equivalent radon concentration (a term defined in Section 1.8 below). 

The concept behind the design of this testing protocol is that the plastic sample is delivered to a mammalian fibroblast culture. Once this exposure is made, the culture is evaluated for signs that the cells are interacting with the plastic or its leachants. Although some reaction is permissible, a subjectively defined upper limit is set beyond which the plastic or elastomeric container or closure will fail the test. The test protocol includes a positive control and a negative control in addition to the sample to assure that the system is valid. 

Toxic conditions. Personal protecdve equipment requirements (including respiratory protection) are based in pan on the concentration of toxic vapor or gas in the air. A toxic atmosphere is defined (by OSHA) as having a concentration which exceeds permissible or published exposure limits (such as the TLV or PEL)... 

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