Glossary of Terms
EVM Series User Manual
REL (Recommended
Exposure Limit)
Exposure limits set by the National Institute for Occupational Safety and Health
(NIOSH).
The relative humidity of an air-water mixture is defined as the ratio of the partial
pressure of water vapor in the mixture to the saturated vapor pressure of water at a
prescribed temperature. This can be calculated by dividing the temperature and dew
point readings and multiplying by 100%.
Toxic and LEL sensors are calibrated to detect a specific gas. However there may be
some cross-sensitivity of the sensor to other toxics or combustibles.
Point in time when the maximum exposure will occur from the beginning of any 8-
hour period
Threshold limit value: the level of exposure that a worker can experience in the
workplace without an unreasonable risk of disease or injury. These are not estimates
of "level of risk" for different exposure levels nor do they address the different means
by which a person may be exposed to a substance. TLV's are specified by ACGIH,
the American Conference of Government Industrial Hygienists. TLV's are guidelines
prepared by ACGIH and are solely concerned with health risk. They do not address
economic considerations. TLV's are not regulatory but rather are advisory. (See PEL
and TWA which are specified by OSHA).
VOC (Volatile Organic
Compound)
A type of air pollution that is a carbon-containing chemical, which is typically
vaporized at ambient temperatures. Some examples of VOCs include: biological
agents (mold, dust, mites…etc.), carbon monoxide, formaldehyde, second hand
tobacco smoke. On the EVM, VOCs are measured in air by using the Photoionization
detection (PID) sensor.
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