Knowledge Centre


COVID-19 Indoor Air Quality


Given the World Health Organisation has now confirmed that COVID-19 survives under certain indoor air conditions for up to 3 hours and its head scientist of disease has urged hospitals to better manage their air quality for staff when treating patients, there is a serious need for the public to understand the impact that air quality and in particular humidification levels can have on the spread of a virus. 


It is recognised that a regular cleaning and disinfection regime in addition to general social distancing intervention decreases the chance of transmitting the virus. However, these controls do not prevent the the airborne transmission of the virus.

There is now an abundance of data that shows that maintaining indoor relative humidity at 40-60% benefits building occupants in several ways:

  • When RH is in this optimal range, infectious aerosols released from a sick person quickly settle out of the air and can be wiped away from surfaces.
  • Many viruses and bacteria carried in droplets are less infectious in this midrange RH zone. Conversely, when indoor air is dry, their infectivity is higher.
  • Relative humidity between 40-60% is the range that optimises the ability of our immune system to fight viral and bacterial infections. When indoor relative humidity is lower, our respiratory immune system is less able to protect us from infectious microbes, even when we maintain perfect hand and surface hygiene.

There is currently no regulation on minimum indoor humidity levels in most commercial buildings in the UK. Building codes have focused on reducing energy consumption which has resulted in lowering the permitted minimum indoor humidity level at the expense of occupant health.

Maintaining indoor humidity levels to the 40-60% sweet spot will decrease exposure to infectious particles and reduce viral illness transmission. 

Facilities managers have a vital role to play in reducing the spread of viral illnesses such as COVID-19. We now know that viruses and bacteria can survive in tiny infectious aerosols that are transmitted in dry air. This brings into focus the importance of properly humidifying and ventilating buildings to reduce transmission of airborne infections. 

While we know that viruses can be spread through physical contact with an infected person, they can also travel in tiny droplets released during a sneeze, cough or even when an infected person breathes, can travel through air into an HVAC system when the air quality in a building is dry. This puts building occupants at increased risk of infection even if they have not come into close contact with an infected person.

Data and research show us that if people in offices, hospitals, and schools manage their indoor relative humidity at 40-60%, human immune mechanisms for physiological defence are improved. Not only does humidifying the indoor environment decrease infectious pathogens in the air we breathe, it also bolsters our own immune systems, which is critical, now more than ever.

Euro Environmental can provide Indoor Air Quality Assessment services if your business needs assistance. We are also able to offer a range of COVID-19 related services such as Air & Surface Surveys and Hygiene Audits to assist your organisation in validating your current COVID-19 controls measures. 

Please don’t hesitate to Contact Us 

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