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Coronavirus Outbreak Explained: Air Conditioners That Recirculate Indoor Air May Increase The Risk Of COVID-19 Transmission, Say Experts

According to experts, COVID-19 has been acknowledged as airborne by WHO which implies that such air conditioning systems that are recirculating the indoor air may spread coronavirus among users even when they are practising social distancing

Coronavirus Outbreak Explained: Air Conditioners That Recirculate Indoor Air May Increase The Risk Of COVID-19 Transmission, Say Experts
  • Airborne transmissions like that of COVID-19 rise in closed rooms: Experts
  • Open a window a bit to have outdoor air entering room, say expert
  • Risks can be reduced with ventilation, better filtration of air: Experts

New Delhi: As COVID-19 cases continue to increase rapidly in the country, experts say that use of such air conditioning systems that mostly recirculate the indoor air can be dangerous as the risk of an increase in the transmission of the infection is more as compared to those air conditioners (ACs) that majorly uses outside air. Experts say that with lockdown being eased in phased manner letting offices to reopen, flights and trains made operational, people are coming together in a closed space with ACs for a longer duration. They say the risk is that any COVID-19 aerosols in the air could be transmitted more easily to people in the room, even if they maintain the recommended physical distance of three feet.

Also Read: COVID-19 Explainer: What Is Far UV-C Light, And Can It Kill The Coronavirus On Surfaces?

While explaining how ACs can increase the risk of transmission, Dr. Preeti Kumar, Vice President- Public Health System Support at the Public Health Foundation of India said,

Essentially, COVID-19 is an airborne disease and so the atmosphere plays an important role in the spread of the virus among the people in that area. When initially, the lockdown started opening up, the central and state governments developed guidelines on how to make industries and offices safe in which there was some discussion around the airflow through ACs. However, as the pandemic grew, the emphasis became far more on the use of a mask and hand hygiene and focus regarding the safety of offices shifted to encouraging people not to touch door handles or lift buttons and other such frequently touched spots. While these practices hold immense value in fighting the pandemic. Now, there are evidences are coming that indoor air where a large number of people gather together becomes a super spreader event. In our country, economic activities and entertainment activities are largely done indoors and most of our buildings in areas where the temperatures are too hot or too cold outdoors are designed in such a way that there is a need to use air conditioners to maintain comfortable temperature indoors.

She further said that when outside temperatures are extreme, some heating, ventilation and air-conditioning (HVAC) systems recirculate the already adjusted indoor air and mix it with some fresh air to become energy efficient but this means that people are inhaling a high amount of the air being exhaled by others in the same room. She said,

ACs have fans that blow the air around, thus producing air current. This air current gives the smallest viral particles, the aerosols, an extra lift to stay suspended in the air for a longer time and travel further than they might otherwise go. Therefore, maintaining social distancing in this scenario will be of no use. The virus can get transmitted easily and so the cases of infection go up.

Also Read: Coronavirus Outbreak Explained: What Is T-Cell Immunity And How Does It Provide Defense Against COVID-19?

Dr KK Aggarwal, President, Confederation of Medical Associations in Asia and Oceania (CMAAO) and Medtalks, Heart Care Foundation of India highlighted the case of Diamond Princess Ship which had a closed central AC atmosphere. He said,

Some researchers have studied air conditioning systems on the Diamond Princess — a 3,700-passenger cruise that was placed on lockdown off the coast of Yokohama, Japan after a passenger disembarked in Hong Kong was later tested positive. They found traces of the SARS-CoV-2 was identified on a variety of surfaces in cabins of both symptomatic and asymptomatic passengers up to 17 days after cabins were vacated on the Diamond Princess. The air conditioning systems are not designed to filter out particles as small as coronavirus allowing the disease to rapidly circulate to other cabins. It’s standard practice for the air conditioning systems of cruise ships to mix outside air with inside air to save energy.

Dr. Aggarwal said that the air conditioning used in cruise ships is like that of hotels. In the central AC system, coronavirus could be transmitted to all the spaces it conditions if return air is used, he asserted.

In aeroplanes, he said, the risk is primarily due to close contact between the passengers while seated and due to touch of surfaces like seats, handles, doors, luggage and others. But air conditioning can be a factor too.

Also Read: Coronavirus Outbreak Explained: What Are The Long-Term Impacts Of COVID-19 On Human Body And The Recovery Process?

Dr. Agarwal further explained that currently, in India with temperatures and humidity still high, people are using ACs and droplets carrying the virus may persist longer in a cold atmosphere. He said,

At cold temperature, the size of the droplet shrinks and these smaller droplets tend to be carried to a longer distance through air current generated by AC system.

Dr. Agarwal suggested that in offices, where split ACs are used, open a window a bit to have outdoor air entering room. In case the office is using window ACs, the outdoor airflow rate should be increased if there is an option otherwise open the window a bit to have more outside air, he said.

Both the experts suggest that said ACs that cannot use 100 per cent outside fresh air must be avoided. They said that the risk can be minimized with higher ventilation rate, superior filtration and sanitisation of the air using Ultra-Violet lights. They recommended that offices using central ACs must minimise the presence of the staff and public visits and should encourage video conferencing. According to experts, home air conditioning units may not pose any additional risk of COVID-19 infection during quarantine if the occupants are not infected and there is no outside contact. World Health Organisation (WHO) also says that a well-maintained and operated HVAC (heating, ventilation and air-conditioning ) system can reduce the spread of COVID-19 in indoor spaces by increasing the rate of air change, reducing recirculation of air and increasing the use of outdoor air. It recommends regular inspection and frequent cleaning of ACs.

Also Read: Coronavirus Outbreak Explained: What Is Convalescent Plasma Therapy And How Effective Is It In Treating COVID-19 Patients?

NDTV – Dettol Banega Swasth India campaign is an extension of the five-year-old Banega Swachh India initiative helmed by Campaign Ambassador Amitabh Bachchan. It aims to spread awareness about critical health issues facing the country. In wake of the current COVID-19 pandemic, the need for WASH (WaterSanitation and Hygiene) is reaffirmed as handwashing is one of the ways to prevent Coronavirus infection and other diseases. The campaign highlights the importance of nutrition and healthcare for women and children to prevent maternal and child mortality, fight malnutrition, stunting, wasting, anaemia and disease prevention through vaccines. Importance of programmes like Public Distribution System (PDS), Mid-day Meal Scheme, POSHAN Abhiyan and the role of Aganwadis and ASHA workers are also covered. Only a Swachh or clean India where toilets are used and open defecation free (ODF) status achieved as part of the Swachh Bharat Abhiyan launched by Prime Minister Narendra Modi in 2014, can eradicate diseases like diahorrea and become a Swasth or healthy India. The campaign will continue to cover issues like air pollutionwaste managementplastic banmanual scavenging and sanitation workers and menstrual hygiene


Coronavirus has spread to 196 countries. The total confirmed cases worldwide are 26,10,35,501 and 51,95,019 have died; 22,18,42,204 are active cases and 3,39,98,278 have recovered as on November 28, 2021 at 3:39 am.


3,45,72,523 8,774Cases
3,39,98,278 9,481Recovered
4,68,554 621Deaths
In India, there are 3,45,72,523 confirmed cases including 4,68,554 deaths. The number of active cases is 1,05,691 and 3,39,98,278 have recovered as on November 28, 2021 at 2:30 am.

State Details

State Cases Active Recovered Deaths

66,33,612 507

11,905 248

64,80,799 738

1,40,908 17


51,29,359 4,741

49,152 957

50,40,528 5,144

39,679 554


29,95,285 322

6,783 143

29,50,306 176

38,196 3

Tamil Nadu

27,24,731 740

8,382 36

26,79,895 765

36,454 11

Andhra Pradesh

20,72,446 248

2,158 5

20,55,856 253


Uttar Pradesh

17,10,373 5

86 5

16,87,377 9

22,910 1

West Bengal

16,14,152 701

7,820 27

15,86,882 717

19,450 11


14,40,834 27

290 11

14,15,448 37

25,096 1


10,48,492 264

2,222 6

10,37,864 255

8,406 3


10,06,733 27

326 7

9,92,814 20



9,54,741 26

187 13

9,45,599 13



8,27,382 28

291 17

8,16,999 45


Madhya Pradesh

7,93,120 23

112 9

7,82,480 14



7,71,654 11

159 1

7,61,441 10



7,26,212 3

39 6

7,16,510 9



6,75,479 160

3,545 11

6,67,946 148

3,988 1


6,16,435 123

2,720 71

6,07,624 189

6,091 5


6,03,190 17

313 22

5,86,284 39



3,49,216 20

109 0

3,43,967 20



3,44,183 14

150 6

3,36,626 8


Jammu And Kashmir

3,36,386 149

1,724 5

3,30,189 141

4,473 3

Himachal Pradesh

2,26,941 82

809 18

2,22,287 97

3,845 3


1,78,839 40

275 9

1,75,183 31



1,34,279 358

4,117 110

1,29,672 466

490 2


1,28,860 35

326 5

1,26,662 30



1,25,117 19

673 1

1,22,474 18

1,970 2


84,784 13

89 9

83,874 3

821 1


84,414 20

308 27

82,635 44

1,471 3


65,443 5

52 4

64,571 1


Arunachal Pradesh

55,269 9

37 4

54,952 5



32,211 4

114 5

31,694 9



32,100 4

135 1

31,269 5



21,494 27

249 6

21,032 21


Dadra And Nagar Haveli


1 0





28 1

10,315 1


Andaman And Nicobar Islands

7,680 2

5 2



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