Is it safe to use air conditioners (ACs) during these Covid-19 times? The question is currently being hotly debated. There is lot of misinformation, and many unverified claims in the public domain. Social media is so abuzz with rumours that experts emphasise the importance of going only by authentic information. With a harsh summer setting in, and the coronavirus still around, people need to be well-informed on the healthy and correct use of ACs.
A special technical task force of The Indian Society of Heating, Refrigerating and Air Conditioning Engineers (ISHRAE) has issued recommendations for operating air conditioning and ventilation systems during the coronavirus. The guidelines put to rest some of the concerns of using ACs at home and heating, cooling and ventilation systems in large commercial spaces, public areas and, more importantly, hospitals where patients are being treated and quarantined.
Vishal Kapur, Chair, Covid-19 Task Force, ISHRAE Technical Committee, in the report, states, “In preparing this document, the Covid-19 Task Force has extracted, examined, analysed and compiled information pertaining to the climatic regions of the Indian Subcontinent. The Team referred to publications in peer reviewed journals and reports from other relevant organisations around the world in arriving at this conclusive guideline.”
The task force notes that concerns have been raised about the likelihood of the spread of the virus through air-conditioning and ventilation systems. Infectious diseases can spread by several different routes, including transmission through air. The questions being asked are whether their spread can be accelerated or controlled by heating, ventilation, air-conditioning and refrigeration (HVACR) systems, depending on how the systems are designed and operated.
According to studies, 80 per cent and above relative humidity tends to neutralise the Covid-19 virus. However, too much humidity leads to higher levels of dust mites and fungi, two of the worst culprits for those suffering from indoor allergies. Also, mould and fungi are known to worsen respiratory conditions such as asthma.
The ISHRAE report states that low temperatures (7–8 °C) are optimal for airborne influenza survival. However, virus survival decreases progressively at moderate temperatures (20.5–24 °C) and further decreases at higher temperatures (greater than 30 °C). As per some recent studies, SARS-CoV-2 has been found highly stable on surfaces for 14 days at 4 °C; for a day at 37 °C and 30 minutes at 56 °C.
The right settings
Says Santosh Salian, Product Group Head, Air Conditioners, Godrej Appliance: “Air conditioners help in providing a controlled ideal environment to mitigate the risk of infections. Various studies have concluded that a relative humidity level between 40 and 70 per cent is the most suitable environment for humans. We recommend you to set the AC’s temperature between 24°C and 30°C. This will help maintain the right relative humidity between 40 and 70 per cent and simultaneously use fans to increase air movement in the room.”
In terms of air-conditioning usage in commercial applications, keeping the temperature between 24°C and 30°C, while ensuring that the air filters and indoor unit coils are clean, washroom and kitchen exhaust fans are operational, and ventilation is adequate, is necessary, says Salian.
The ISHRAE report, in addition to describing the coronavirus and its transmission routes, looks at the effect of environmental conditions such as relative humidity and temperature in residential, commercial and industrial applications and seeks to provide some clear norms.
In the case of healthcare facilities, it has come up with several dos and don’ts to ensure safety of patients and other hospital staff. For commercial and industrial facilities, it suggests as much ventilation with outdoor air as possible. One of the concerns is that most commercial establishments have remained shut amid lockdown and would require maintenance. Unless proper care is taken, they could pose health hazards with fungus and moulds developing in the ducts and open spaces. Bird droppings, excreta of rodents and insects is another area that needs effective tackling.
Effective use of air-conditioning during a pandemic is a matter of ongoing research. Points out Himanshu Agrawal, Founder, CEO, Magneto CleanTech, “Continued research is bringing to light facts about the novel coronavirus, one of the most disturbing ones is its airborne nature. The medical world strongly suspects that the virus can be spread through air, especially when it is already contaminated with various pollutants like dust, bacteria and microbes. Air-conditioned places are at a higher risk as ACs are known to enable infection transmission. It is a myth that the AC keeps air clean. It only cools the air and recirculates it.”
According to him, a larger centrally air-conditioned place is even more dangerous since it further distributes already contaminated air from outside to various parts of the building which usually has no sunlight but has other gaseous pollutants from the furniture, paint, etc. These are all mixed and distributed in a central air cooling AHU (air handling unit) chamber and not many are equipped with high efficiency air filtration and UVGI (ultraviolet germicidal irradiation) technologies.