Appendix D. Infrared Light and Eye Safety

This section summarizes some ideas and thoughts that were exchanged on the Linux/IrDA mailing list. It is not medically well-founded, and whoever has better evidence or some more well-founded source of information is encouraged to contribute it to this HOWTO.

The IrDA spec says that the range of IrDA devices has been limited to 1m for reasons of eye safety. Another plausible assumption is that power consumption and IR pollution/crosstalk were reasons for this limitation. In principle there could be danger for the eye, because infrared light is not registered by the eye, and thus the pupil won't close in order to protect the retina from bright IR light sources. This is the same situation as with UV light, which will cause snow blindness eventually, but in contrast to UV light, IR light contains much less harmful energy due to its longer wavelength.

The only legal restrictions and medical advices we were able to find on the web were concerned with infrared emissions of heat lamps or in the welding process and IEC 825-1 (CENELEC EN60825-1). This suggests that IR light as emitted by IrDA devices will be harmless, since even the peak power emitted by strong IR LEDs (ca. 300mW) is several orders of magnitude below the power emitted by medical IR heat lamps (up to 500W). For these, however, you are supposed to wear protective goggles, so maybe if you are looking straight into 1.000 infrared LEDs flashing at once, you should do so, too. The effect of infrared light is mostly heat, though, and not an alteration or destruction of the biological cell structure, such as caused by UV light. Though in the specs for the HP OmniBook 800 Hewlett-Packard recommends not to look directly into the IR LED.

As stated above, this discussion is only based on guesswork and common sense assumptions about the data found in IR LED and heat lamp specs. If anybody with a better medical knowledge can comment on this, please do so!