Glossary of Terms: I

IARC
International Agency for Research on Cancer.
Ignition source
A source of energy, such as heat, flame, sparks or static electricity that is capable of causing a fuel mixture to burn or explode.
Ignition temperature
The lowest temperature that will cause a mixture to burn or explode.
Immediately Dangerous to Life and Health (IDLH)
An atmospheric concentration of any toxic, corrosive or asphyxiant substance that poses an immediate threat to life or would cause irreversible or delayed adverse health effects or would interfere with an individual's ability to escape from a dangerous atmosphere.
Impervious
A material that does not allow another substance to pass through or penetrate it. Frequently used to describe gloves.
Inches of mercury column
A unit used in measuring pressures. One inch of mercury column equals a pressure of 1.66 kPa (0.491 psi).
Inches of water column
A unit used in measuring pressures. One inch of water column equals a pressure of 0.25 kPa (0.036 psi).
Incompatible
Materials which could cause dangerous reactions from direct contact with one another.
Industrial hygiene
A science that deals with the anticipation, recognition, evaluation, and control of hazards in the workplace. These hazards may cause sickness, harm to employee health, discomfort, and inefficient performance on the job. Also known as occupational hygiene.
Infrared detector
Gas detector that uses the principle that infrared light is absorbed by gas molecules at specific frequencies.
Ingestion
Taking in by the mouth. The swallowing of a substance.
Ingress protection (IP)
A measure of protection against the ingress of dust and water.
Inhalation
Breathing of a substance in the form of a gas, vapor, fume, mist, or dust.
Injection
To force or drive liquid or gas into the body.
Insoluble
Incapable of being dissolved in a liquid.
Integrating threshold
(aka Cutoff) The threshold affects the Lavg, TWA, and Dose measurements. All sound below the threshold is considered nonexistent noise for the averaging and integrating functions. The threshold does not affect measurements in the sound level mode. OSHA uses two different thresholds. The original Occupational Noise Exposure Standard (1971) used a 90dB threshold and called for engineering controls to reduce the noise levels if the eight-hour TWA was greater than 90dB. The Hearing Conservation Amendment (1983) uses an 80dB threshold and calls for a hearing conservation program to be put in place if the eight-hour TWA exceeds 85dB (50% dose). The Hearing Conservation Amendment is the more stringent of the two rulings and is what most US industrial users are concerned with. Because real noise fluctuates, it is quite possible to have an average level below the threshold. This also applies for the overall Lavg.
Intrinsically safe (IS)
Approval by an appropriate authority to use the instrument in hazardous area. Method of design so that the maximum internal energy of the apparatus and wiring is not sufficient to cause ignition by sparking or heating effects resulting from a fault.
Irritant
A non-corrosive substance which, in sufficient quantities, can inflame or irritate the eyes, skin or respiratory system (lungs, etc.), by chemical action at the site of contact. Symptoms include pain and reddening.