HUMIDITY CONTROL
Reducing risk of infection
Humidity control is important in all working and living spaces but is of particular signifi cance in ‘clean’ areas requiring eff ective infection control. John Barker of Humidity Solutions explains.
T
he relationship between relative humidity (RH) and comfort and wellbeing is well-recognised, with most authorities recommending that RH is maintained between 40% and 70% in workplaces and homes. Conditions outside this range have the potential to cause a range of health problems and can also result in damage to building fabric.
What is not so widely known is the relationship between RH and pathogens such as viruses and bacteria and the implications for infection control. In most workplaces this is not a major issue but in many healthcare and pharmaceutical facilities, where infection control is of paramount
44 September 2017
importance, humidity control needs to be a priority.
RH and airborne pathogens
Exposure to viruses can occur in one of three ways: touching contaminated surfaces, direct exposure to large droplets or inhalation of smaller droplets. Speaking, coughing or sneezing expel large numbers of ‘aerosols’, which are suspensions of solid or liquid particles in air. The smaller the particles, the longer they remain airborne and can therefore travel further. A signifi cant proportion of the expelled particles are between fi ve and 10µm in diameter
but when exposed to dry air much of the moisture will evaporate almost instantly, so that the particles reduce in size and therefore remain in the air for longer. This means the viruses can travel further in dry air, thereby increasing the risk of infection across a wider area. In more humid air the hygroscopic nature of these particles will cause them to group together, forming larger particles that fall to a surface more quickly. This increases the eff ectiveness of regular cleaning of surfaces as part of an infection control regime.
In addition, research has shown that viruses such as infl uenza and norovirus (the ‘vomiting
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