Page 24 - Climate Control News Magazine Feb 2020
P. 24

Understanding the science
behind humidity and health
CONDAIR AUSTRALIA BUSINESS DEVELOPMENT MANAGER, IAN EITZEN, EXPLAINS THE IMPACT OF LOW HUMIDITY ON OUR HEALTH.
LEFT: Condair Australia’s Ian Eitzen.
ABOVE: Studies show atmospheres maintained at above 40%RH curtail the airborne viruses.
UNDER THE WORK Health and Safety Act 2011, employers have a duty of care to provide the highest level of protection against harm to health and welfare from risks aris- ing in the workplace, so far as is reasonably practicable. Many organisations in the building services industry, including CIBSE and BSRIA, recommend that the ideal indoor humidity for health is in the range 40-60%RH.
So how great is the risk to health if an indoor hu- midity falls outside of these conditions and is it rea- sonably practicable to expect an employer to take steps to maintain a “healthy” indoor humidity?
Scientific research into the effects of humid- ity on the air, specifically with regards airborne infection, was being carried out as early as the 1930’s and 40’s. Early experiments with mice, by Loosli et al in 1943, showed airborne flu re- mained active and infectious for much longer at low humidity under 40%RH. More recent stud-
ies around the same hypothesis by Noti et al in 2013, used mechanical nebulizers to “cough” flu virus into a room at varying humidity levels, and air samplers to assess its infectious nature. The results were similar and demonstrated a dramatic drop in the flu virus’ ability to survive in air at more than 40%RH.
Numerous other studies, taking place between these two, have also shown that atmospheres maintained at above 40%RH significantly curtail the airborne transmission of flu and other viruses. A review of over 20 such investigations since 1960, carried out by Jane Metz and published in the Journal of Infection in 2015, concluded that “the prospect of reducing inf luenza-associated mor- bidity and mortality by increasing the absolute humidity in ... public spaces is an exciting and novel potential strategy for disarming ‘flu”.
Two reasons are put forward to explain the detrimental effect humidity has on airborne germs. Firstly, it’s been shown that droplets re-
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