This is how you can safely use air-conditioners during the pandemic
Studies probing the role of air conditioners in the spread of covid-19 suggest they are safe as long as the rooms have regular ventilation
On 1 February, a passenger on the British cruise liner Diamond Princess, who had disembarked in Hong Kong seven days earlier, was found infected with covid-19. Within days, the operator, Princess Cruises, cancelled the trip and docked on the Japanese coast. The passengers were asked to self-quarantine in their cabins, with Wi-Fi, meals and other facilities taken care of by the staff. And yet, two weeks later, 542 of the 2,666 passengers tested positive for the virus.
There are several theories about why the virus spread. Perhaps passengers didn’t follow the safety guidelines strictly, perhaps they had already been exposed to the virus before the quarantine began, or perhaps it came from the staffers who continued serving the guests in their rooms —19 of them later tested positive. A particularly disturbing theory was that the virus spread through the ship’s centralized air-conditioning system. The lack of air-filtration mechanism meant it infected even those who followed the safety measures.
The theory gained traction quickly. When India announced a lockdown from 25 March, Maharashtra chief minister Uddhav Thackeray, citing guidelines from the Union government, implored people to restrict their air conditioner (AC) usage. A month later, the Haryana government too asked users to minimize the use of ACs. In April, researchers from China, who had studied the spread of the virus to 10 diners of a restaurant in Guangzhou, attributed the spread to the centralized air-conditioning system. Strong airflow from the restaurant AC, the study said, could have directed the covid-19 droplets to tables in the same row as the index patient’s.
While the authors of this study admit to its limitations, AC users in India, where summer was setting in, didn’t know what to believe. They were worried about home as well as office use.
Since sales had stopped, the market didn’t register the impact. But according to Google Trends, “Is AC safe during coronavirus" was among the top 3 Google searches in April.
A number of studies and guidelines since have thrown light on the issue. In April, guidelines issued by the Indian Society of Heating, Refrigerating and Air Conditioning Engineers (Ishrae) recommended a temperature setting of 24-30 degrees Celsius and humidity setting of 40-70%. Instead of the same air recirculating, users were asked to keep windows open slightly to allow outdoor air in or exhaust by natural exfiltration.
A Federation of European Heating, Ventilation and Air Conditioning Associations (Rheva) study, released a few weeks after Ishrae’s guidelines, doesn’t quite agree with the Ishrae-recommended humidity and temperature. Virus viability would be impacted if the relative humidity is above 80% and temperature above 30 degrees Celsius, it says—neither makes for comfortable indoor air. Like Ishrae, however, it too recommends opening up rooms regularly, along with regular maintenance of the AC systems.
The bottom line, it seems, is that ACs can be safe for use in commercial spaces as long as adequate precautions are taken. In a residential setting, they pose no threat as long as the ones you share the space with aren’t infected.
When Indian Railways partially resumed operations earlier this month, it too clarified the role of ventilation in air-conditioned spaces. “As per Ministry of Health guidelines, centralised AC is acceptable, provided complete air change inside an AC coach takes place at least 12 times per hour," it said in a statement. “We are ensuring that our system replaces air more than 12 times per hour." Before flight operations were allowed to resume from 25 May, aviation experts flagged the role of air direction, saying there is little chance of cross contamination since there is downward airflow inside cabins.
Soon after, the studies and guidelines, the AC manufacturers swung into damage control mode.
As a first step, they started putting out publicity material to remove misconceptions. “We advertised in newspapers, on social media, and sent out a large number of SMSes to our customers," says Gurmeet Singh, managing director of Hitachi India and president of Refrigeration and Air-conditioning Manufacturers Association (RAMA), which represents most leading AC manufacturers in India. “We also sent letters to all PWD (public works) departments, giving our understanding (of the issue)."
The outreach worked. Two weeks after Ishrae issued its guidelines, the Central public works department (CPWD) issued an identical set of guidelines.
Some authorities remain unconvinced, though. Uttar Pradesh has allowed malls outside Lucknow to open without centralized air conditioning. Tamil Nadu, too, has forbidden salons and beauty parlours from using ACs. According to news reports, a number of companies are recognizing such concerns and investing in upgrading their ACs to adjust filters and airflow systems.
By 18 May, or “Lockdown 4.0" as it’s known, the ban on sale was lifted and shops selling ACs were allowed to open in areas not marked as red zones. But by then, most manufacturers had lost weeks of peak-sale season.
The months of March-June account for over 30% of annual sales for the AC industry. No sales during this period may have cost the industry a little under Rs20,000 crore, claims Singh. As the electronics markets open up, most manufacturers are expecting the AC link to covid-19 spread to come up in conversations with customers.
“We have done a huge number of webinars with our staff to address questions about safety," says Singh. “At the moment, we are planning to put out more communication on this matter. When you talk more about it, it spreads more." The misconception, that is, not the virus.
FIRST PUBLISHED27.05.2020 | 09:20 AM IST