Connect with us

Coronavirus Explainers

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

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 195 countries. The total confirmed cases worldwide are 22,70,55,138 and 46,70,253 have died; 18,97,86,461 are active cases and 3,25,98,424 have recovered as on September 17, 2021 at 5:36 am.


3,33,81,728 34,403Cases
3,25,98,424 37,950Recovered
4,44,248 320Deaths
In India, there are 3,33,81,728 confirmed cases including 4,44,248 deaths. The number of active cases is 3,39,056 and 3,25,98,424 have recovered as on September 17, 2021 at 2:30 am.

State Details

State Cases Active Recovered Deaths

65,11,525 3,595

52,893 310

63,20,310 3,240

1,38,322 45


44,46,228 22,182

1,86,754 4,559

42,36,309 26,563

23,165 178


29,65,191 1,108

16,202 282

29,11,434 808

37,555 18

Tamil Nadu

26,40,361 1,693

16,756 120

25,88,334 1,548

35,271 25

Andhra Pradesh

20,34,786 1,367

14,708 105

20,06,034 1,248

14,044 14

Uttar Pradesh

17,09,628 23

193 11

16,86,549 11

22,886 1

West Bengal

15,59,567 707

8,025 25

15,32,922 725

18,620 7


14,38,373 28

409 5

14,12,880 22

25,084 1


10,18,298 580

5,335 105

10,04,845 681

8,118 4


10,04,988 31

352 2

9,91,077 29



9,54,230 4

103 1

9,45,173 5



8,25,677 22

149 0

8,15,446 22


Madhya Pradesh

7,92,374 7

119 5

7,81,738 12



7,70,697 9

327 8

7,60,562 17



7,25,864 12

72 6

7,16,134 6



6,62,785 259

5,282 43

6,53,603 301

3,900 1


6,01,180 30

314 11

5,84,399 38

16,467 3


5,97,074 468

5,381 15

5,85,914 479

5,779 4


3,48,102 6

102 8

3,42,867 14



3,43,330 20

284 12

3,35,657 32


Jammu And Kashmir

3,27,466 170

1,421 72

3,21,630 98


Himachal Pradesh

2,16,430 127

1,568 82

2,11,215 206

3,647 3


1,75,183 95

699 1

1,71,195 96



1,25,170 107

963 63

1,22,380 42

1,827 2


1,17,913 216

2,614 7

1,13,478 219

1,821 4


83,787 31

427 26

82,553 56

807 1


78,958 229

1,804 140

75,784 86

1,370 3


76,591 1,121

13,888 85

62,449 1,202

254 4


65,168 4

31 2

64,319 2


Arunachal Pradesh

53,990 47

536 9

53,183 56



30,802 64

775 28

29,648 36



30,763 32

505 14

29,610 44

648 2


20,631 6

41 1

20,383 5


Dadra And Nagar Haveli


5 0





4 0



Andaman And Nicobar Islands

7,595 3

15 2

7,451 1


Coronavirus Outbreak: Full CoverageTesting CentresFAQs

Leaving No One Behind

Mental Health


Join Us