The office, air conditioned in the summer and heated in the winter, is often the number one place where we will be exposed to dry air and the problems it causes us. As human beings, we are far less sensitive to dry air than we are to temperature and we commonly fail to associate the discomfort or health problems we experi-ence at work with low relative humidity.
Office Humidity Issues
Several professional bodies produce guidelines on appropriate humidity levels in the office and commercial premises. CIBSE, BSRIA and BRE generally agree that the appropriate range of RH in an office environment should be around 50%RH, within a typical range of 40-60%RH, a figure endorsed by HEVAC.
In the UK, the Health and Safety Executive's Display Screen Equipment Regulations 1992, obliges emplyers to maintain a level of realative humidity that prevents discomfort and problems of sore eyes where people work at computer terminals for long periods, a situation which affects a high proportion of office staff.
Eyes are susceptible to low humidity as the thin layer of moisture on the cornea rapidly evaporates. Contact lens wearers express discomfort that can increase by a factor of five as humidity drops from 45% to 20%, by which stage dust and dirt deposits an lenses increase causing greater irritation.
One of the first noticeable effects of dry air is electrostatic shocks, which occur below a threshold of 40%RH. This is not only an annoying nuisance to people working in the office but it can also damages sensitive computer equipment.
People feel warmer and more comfortable at the right humidity and are less sensitive to bad smells.
A study carried out by a major mineral water company revealed that of the 500 UK workplaces examined in the survey, one in five offices were as dry as the Sahara desert, with 25% relative humidity, and one in ten as dry as California's Death Valley, with only 23% relative humidity.
To maintain the RH at the appropriate level, it is necessary to add water to the air artificially using a humidifier. Using mobile or wall-mounted humidifiers in the office itself is an option but it is typically more convenient and effective to include them in a building's air conditioning air handling systems.