FAQ on Environment

Q: How the relative humidity (RH) affects ESD events?

A: In general the ability for static charges to cumulate on materials is diminish when the RH is high, say between 50% and 60% as such an ambient will favour the leaking of charges from materials into the surrounding air. However there is a limit to how high can you go, say at 80% electronic devices are likely to corrode easier and bridging short circuits can occur in dense populated PCB. If the RH is too low, say 30% due to triboelectric activity static charges will grow faster as there will be no enough conductivity in the air to allow for charges to dissipate. Also a very uncomfortable situation for personnel as casual touching or touching of objects may give them painful ESD discharges, not uncommon to be in the range of 30kV to 50kV, also staff may complaint of dry nose and/or throat.

Q: What is condensation?

A: Condensation occurring where electronics equipment is installed may be destructive and must not be allowed. Condensation occurs when we have simultaneously high temperature and relative humidity in a site but where the temperature varies suddenly in small steps. Standards specify maximum gradients of change in temperature (<1ºC/6min) and a relative humidity (<10%/hr). As a guide in the telecommunications industry 20ºC is said to be comfort zone for electronic equipment and 25ºC for humans, hence pending of the number of people in a site the temperature setting can be adjusted accordingly. Standards indicate a larger acceptable variation for rooms where there is operational equipment, say 16ºC to 32ºC (optimum 23ºC+/-2ºC) and 40% to 70% (optimum 50+/- 10%).