|MadSci Network: Environment|
Hi Marsha, Humans, and every other organism, survive within a species specific range of environmental tolerances. Survival tolerances exist for all environmental conditions including pH, temperature, noise, U.V. radiation and obviously humidity. In a simple example this is why you don't see polar bears in the tropics nor cactus in a rain forest. It is also why it is so hard for fish lovers to set up a marine fish tank - the bandwidth of tolerances for these fish are so small. As humans we stretch the survival tolerance. Through tools, clothing and invention we manage to survive in the hotest deserts as well as at the poles. We thrive in everything in between. Unfortunately these inventions include crazy 6" high heels for women, chemicals on our skin and in our diet, not to mention artificial lighting and air conditioning in our workplaces. None of which are really geared toward our natural tolerances or physical design. In answering your question, there are several affects of humidity on us as humans. An example is people suffering from heat stress in high temperature, high humidity, manual labour. One of our most effective natural cooling systems is the use of sweat which is released onto our skin and evaporates away taking with it heat energy. High humidity reduces this evaporation and therefore interferes with our cooling, potentially resulting in debiliating sickness and even death. As far as indoor requirements I checked the Australian Standard 1668:2002 (The use of ventilation and airconditioning in buildings) which states that it does not prescribe humidity requirements for buildings - no luck there. However, according to air purifier suppliers (www.secondwindairpurifiers.com) and some unknown authority ASHRAE (possibly American - I am Australian) humidity under 25% "is associated with increased discomfort and drying of the mucous membranes and skin" while "high humidity can result (in)... the ... development of mold and fungi along with the increase of dust mite propagation". Seems both high and low humidity could cause breathing problems in sensitive people. Being an undergrad I suggest you take the opportunity to practice your skills in ensuring the validity of your sources and get onto the supplier's website and find out who ASHRAE are and, if they are a recognised expert body or government agency, check out a copy of their standards. Good luck. Peter
Try the links in the MadSci Library for more information on Environment .