Infra-red radiation, also known as IR, is named because the wavelength is slightly longer than red light in the visible light spectrum.
Infra-red is usually divided into near (IR-A), mid (IR-B) and far-infrared (IR-C) regions;
• Near IR-A: 700 nm–1400 nm (215 THz - 430 THz) and the region closest in wavelength to the red light visible to the human eye
• Mid IR-B: 1400 nm–3000 nm (100 THz - 215 THz)
• Far IR-C: 3000 nm–1 mm (300 GHz - 100 THz)
Mid and far-IR are progressively further from the visible spectrum and nearer to microwave radiation.
There are two potentially significant hazards associated with IR radiation:
- Thermal effects.
Infrared waves are given off by all warm objects and produce heat in all objects they strike. The waves cause heat by exciting molecules (increasing their movement) in the substances they strike. The earth is warmed by infrared radiation from the sun.
Sources of IR radiation are used as artificial heating devices e.g. printing ink driers, food warmers in restaurant kitchens, cold weather outdoor heaters and for therapeutic heat treatments. These present minimal risks of harm to health, but other sources of IR from ‘hot’ work applications such as work with molten metals, welding and glass blowing can cause serious burns to unprotected skin.
- Eye effects.
The use of furnaces, powerful heating and drying processes and high powered LED's which use IR can result in cataracts developing and flash burns to the cornea - these are the main biological effects of IR-A radiation due to temperature rise in the tissue. But IR-A radiation wavelengths are close to the visible light wavelengths and are transmitted to a small extent to the retina; permanent retinal damage can occur if the source is high powered (produces heat) and the exposure is prolonged. As wavelengths increase into the IR-B and IR-C regions the radiation is no longer transmitted to the retina but corneal flash burn injuries can still be caused.
Where a work activity is known or suspected to generate significant IR radiation, a risk assessment must be carried out and control measures put in place. The supplier or manufacturer of the IR source will be able to provide technical information on the power, flux density etc. to allow an informed assessment to be carried out.
Typical control measures are provision of enclosures and shielding around the source to prevent exposure, use of protective clothing to prevent skin exposure and use of IR-opaque eye protection to prevent eye exposure.