ASHRAE Humidity Guidelines For Reopening Schools & Unis

The ASHRAE Epidemic Task Force has recently published guidance on the operation of HVAC systems in schools and universities, to mitigate the airborne transmission of SARS-CoV-2. This is in preparation for the reopening of schools in the new academic year. The ASHRAE recommended winter classroom design condition specifies 40-50%RH through proactive humidification, either via AHUs or directly in the classroom.

Dave Marshall-George, UK Sales Manager at Condair plc, comments, “It is very reassuring to see guidance from an authority such as ASHRAE including a recommendation for 40%RH as a minimum level of indoor humidity. The infection control benefits of keeping indoor air at above 40%RH have been proven in many scientific studies. ASHRAE’s Epidemic Task Force has taken this very positive step in recognising this science and specifying humidifiers ought to be used in educational establishments during the winter, for the health and protection of pupils and staff.

“Without humidification, indoor humidity will typically drop below the important 40%RH threshold when the outside air is approximately 11°C. In the UK this is happening from around October through to March. Educational establishments, such as schools, colleges and universities are key battlegrounds in preventing the spread of COVID-19, or indeed other respiratory infections, such as the flu. Winter humidification is an effective weapon against respiratory infection. Indoor humidity of between 40-60%RH keeps the body’s respiratory immune system operating efficiently, whilst also decreasing the quantity of airborne viruses and their infectious nature.” Dave continues.

“We very much hope to see this recommendation being taken seriously by the UK authorities and industry bodies. It follows similar advice from CIBSE in its COVID-19 Ventilation Guidance that “relative humidity should be kept above 40%”. The commercial humidifier manufacturing sector is ready to step-up and play its part in the fight against COVID-19 but educational establishments must act now if they are to be ready for the winter. We frequently work with universities to humidify research labs, archives and offices but humidity control in lecture halls and classrooms is extremely uncommon.

“Humidification is a practical, natural and non-pharmaceutical intervention against respiratory infection and we hope to see similar, clear guidance for healthcare premises and office buildings shortly.” Dave concludes.

ASHRAE is the American Society of Heating, Refrigerating and Air-Conditioning Engineers, an association seeking to advance heating, ventilation, air conditioning and refrigeration systems design and construction. ASHRAE has more than 57,000 members in more than 132 countries worldwide. The ASHRAE Epidemic Task Force has been established to help deploy ASHRAE’s technical resources to address the challenges of the current pandemic and future epidemics as it relates to the effects of heating, ventilation, and air-conditioning systems on disease transmission in healthcare facilities, the workplace, home, public and recreational environments. The complete 41-page presentation from ASHRAE on the guideline can be found here.

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