Central ACs should run 2 hrs before office opens: Haryana govt advisory

Adopting new central guidelines prepared by central public works department (PWD), the state government said if running central air-conditioning becomes unavoidable, then air-handling units (AHUs) of central ACs should run on maximum fresh air two hours prior to the opening of office and two hours after the closing to ensure that no contamination remains.

Sounding a word of caution on the use of central air-conditioning in institutions and malls in view of the prospects of Covid-19 spread, the Haryana government on Thursday said it is advisable to avoid central air-conditioning to the extent possible.

The guidelines also said that AHUs are advised to be operated on maximum fresh air and heat recovery wheels should not be used at all. (Representative Image)

Adopting new central guidelines prepared by central public works department (PWD), the state government said if running central air-conditioning becomes unavoidable, then air-handling units (AHUs) of central ACs should run on maximum fresh air two hours prior to the opening of office and two hours after the closing to ensure that no contamination remains.

AHUs are the lungs of a heating, ventilation and air conditioning (HVAC) system. It is a device used to regulate and circulate air as a part of HVAC system. It takes outside air, filters it, cool or heat it and supply it as fresh air to the air-conditioned area.

The guidelines also said that AHUs are advised to be operated on maximum fresh air and heat recovery wheels should not be used at all. Experts said that thermal wheels allow transfer of heat between two adjacent airflows and help in saving energy. The air being expelled is used to cool the hot incoming air during summers using thermal wheels.

The best cooling options without aiding infection or contamination are window-fitted desert coolers, window and split ACs, fans aided by maximum fresh air intake by opening doors and windows and supported by air replacement through exhaust fan facilities in nearby areas, stated the new guidelines. Maximum caution should be exercised to minimise the chances of spread of Covid-19 through airflow in enclosed spaces like residences, offices, meeting and assembly places, the guidelines added.

Guiding principles for running air coolers and air conditioners

Temperature settings of all air conditioning devices should be between 24-30 °C

Relative humidity should be 40-70%

Fresh air intake should be ensured

Re-circulation of air should be avoided

Ensure adequate cross ventilation

Replace air using exhaust fans

Air sanitisation should be frequent done by regularly cleaning and sanitising filters of indoor units

Avoid being in direct line of airflow

Decontaminate surfaces frequently

Observe social distancing norms

A recent research report by Center for Disease Control and Prevention, Guangzhou, China discussing the Covid-19 outbreak associated with air conditioning in a restaurant concluded that in this outbreak, droplet transmission was prompted by air-conditioned ventilation.

“The key factor for infection was the direction of the airflow. One patient was afebrile and 1% of the patients in this outbreak were asymptomatic, providing a potential source of outbreaks among the public. To prevent spread of coronavirus in restaurants, we recommend strengthening temperature-monitoring surveillance, increasing the distance between tables, and improving ventilation,” the report has suggested.