Glossary of Terms: C

CA
An SPL average that enhances the low frequency components of the sound signal. The measurement is used to evaluate hearing protection and other noise reduction devices.
Calibration
The process of adjusting the output of the detector to give an accurate reading of gas concentration over its measuring range.
Capture envelope
A zone in front of a hood within the bounds of which contaminants will move into the hood
Capture velocity
Air velocity at any point in front of a hood necessary to overcome opposing air currents and to capture the contaminated air at that point by causing it to flow into the hood
Carbon monoxide
A colorless, odorless toxic gas produced by any process that involves the incomplete combustion of carbon-containing substances. It is emitted through the exhaust of gasoline powered vehicles.
Carcinogen
A chemical, physical or biological agent capable of causing or producing cancer in mammals, including humans. A chemical is considered to be a carcinogen if a) it has been evaluated by the International Agency for Research on Cancer (IARC) and found to be a carcinogen or potential carcinogen; or b) it is listed as a carcinogen or potential carcinogen in the Annual Report on Carcinogens published by the National Toxicology Program (NTP) (latest edition); or c) it is regulated by OSHA as a carcinogen.
Carcinogenic
Capable of causing Cancer.
CAS number
Chemical Abstracts Service. CAS Registry number used to identify substances without the ambiguity of chemical nomenclature.
Catalytic sensor
For detection of combustible gases. These are made of an electrically heated platinum wire coil, covered first with a ceramic base such as alumina and then with a final outer coating of palladium or rhidium catalyst dispersed in a substrate of thoria.
CE
Indicates compliance to all relevant European directives
Ceiling limit (C)
An airborne concentration of a toxic substance in the work environment, which should never be exceeded.
Cell
An individual sensor.
CENELEC
Comite Europeen de Normalisation Electrotechnique.
Center frequency
The center frequency of each octave and third octave filter band.
CFM
unit of air flow measurement, cu. ft. per minute
Channel
One line or point of detection or input
Chemcassette®
Honeywell registered name of a paper tape cartridge used in toxic gas analyzers.
Chemical agent
A chemical substance that affects the body, a part of the body, or any of its functions. The effects may be beneficial or harmful.
Chemical cartridge respirator
A respirator that uses various chemical substances to purify inhaled air of certain gases and vapors. This type respirator is effective for concentrations no more than ten times the TLV of the contaminant, if the contaminant has warning properties (odor or irritation) below the TLV.
Chemisorption
A non-reversible chemical process, impregnated activated alumina media attracts gaseous contaminants which are converted to non-toxic solids that remain on the pellets and are permanently removed from the environment Differential pressure
the difference in static pressure between two locations, e.g., above and below a filter
Chronic Effect
An adverse effect or change that occurs in the body over a relatively long time (weeks, months, years) following repeated exposure or a single over-exposure to a substance. Also called an acute effect
Chronic Exposure
Repeated exposure to a hazardous agent.
Class 1/Class 2 microphones
See "Type 1/Type 2 microphones".
Code of Federal Regulations (CFR)
A collection of the regulations that have been promulgated under United States Law.
Combustible liquid
Combustible liquids are those having a flash point at or above 37.8°C (100oF).
Combustible
Capable of catching fire and burning, usually a material that has a flash point above 37.8°C. See also flammable.
Community Noise Exposure Level (CNEL)
The CNEL is a 24-hour average sound level, which adds 5dB to noise measured between 7 p.m. and 10 p.m., and adds 10dB to noise measured between 10 p.m. and 7 a.m.
Concentration
The amount of a given substance in a stated unit of measure. Common methods of stating concentration are percent by weight or by volume, weight per unit volume, normality, etc.
Conduit
Metal tubing mainly used in the US for installation of wires in hazardous areas.
Contaminant
An unwanted material (for example, radioactive, biological or chemical) that is likely to harm the quality of the working environment. The most common workplace contaminants are chemicals that may be present in the form of dusts, fumes, gases or vapors.
Controls
Measures designed to eliminate or reduce hazards or hazardous exposures. Examples include engineering controls, administrative controls, personal protective equipment. Hazards can be controlled at the source, along the path to the worker, or at the worker.
Corrosive
A substance that causes visible destruction or permanent changes in human skin tissue at the site of contact.
COSHH
Control of Substances Hazardous to Health.
Crest Factor
The ratio of the instantaneous peak value of a wave to its RMS value. This is a performance specification of a meter’s ability to process signals that have peaks that are substantially higher than their RMS averages.
Criterion Level (CL)
Criterion level is the average SPL that will result in a 100% dose over the Criterion time, usually 8 hours. The Criterion Level is typically set by a regulating agency, such as OSHA, and is not usually applicable for community noise monitoring.
Criterion Time (CT)
The time over which the Criterion Level is established, generally 8 hours.
CSA
Canadian Standards Association.
Cutaneous
Pertaining to or affecting the skin.