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The Covid-19 pandemic has forced people to stay at home. But for every citizen, it is not always a viable option - especially for frontline workers like doctors, nurses and other healthcare professionals.

A section of people is still attending offices - either rotationally or every day. In that situation, it is an additional responsibility to secure the closed-door office environment. These workplaces may not be well ventilated. The two major modes of coronavirus transmissions are through respiratory droplets and through direct contact with contaminated surfaces (fomites).

Discourse on airborne transmission of the virus

The evidence for airborne transmission of coronavirus is not yet proven scientifically. Studies are being performed. Two hundred and thirty nine doctors have already submitted a letter to the World Health Organisation (WHO) stating that they feel the virus is airborne.

A paper titled ‘How can airborne transmission of COVID-19 indoors be minimised?’ that is to be published in the Environment International journal, informed, “Four of these studies found several positive samples for the SARS-CoV-2 genome (RNA) in air using the polymerase chain reaction (PCR) testing, two found very small numbers of positive samples and only one found no positive air samples. This evidence at least demonstrates a potential risk for airborne transmission of SARS-CoV-2.”

The paper also mentioned that a study found positive air samples in two of the three patient infection isolation rooms. The research added, “The study from University of Nebraska, USA found that 63% of the air samples were positive with a mean viral load of 2.9 copies/L, including in patient rooms and the hallway air.”

A report titled ‘Covid-19 Pandemic: Prevention and Protection Measures to Be Adopted at the Workplace’ has mentioned the possibility of the aerial transmission. The report cited a paper named ‘Potential Factors Influencing Repeated SARS Outbreaks’ and informed, “Various evidences have shown how coronaviruses, including the viruses responsible for SARS and MERS, can persist, in optimal conditions of low humidity and low temperature, for up to nine days on the inanimate surfaces of all shared rooms, especially bathrooms, changing rooms, canteens, rooms with distributors, smoking areas, and offices shared with several people. A role of contaminated surfaces in the transmission of SARS-CoV-2 infection is therefore to be considered as being possible, even if not yet demonstrated.”

Dr. Subhrojyoti Bhowmick, Clinical Director, Academics and Research, Peerless Hospitals, Kolkata, told BE, “Before coming to any conclusion regarding a critical topic like this, we must focus on the quality of the study and the adequacy of the evidence. But ICUs and wards of hospitals are truly under the risk zone. Patients who have respiratory distress have to be nebulised. These are highly infected areas. But beside the study made by the University of Nebraska, there are few negative studies that are saying coronavirus is not airborne. For example, Dr. Faridi S. has studied the open field indoor air measurement of SARS-Covid-19 in a patient room in a large hospital in Iran. He did not find viable coronavirus in the air there. Dead coronavirus virus cannot infect other people in the same location. But we must always be careful about the air in the patients’ rooms. Wearing masks should be followed by all to avoid unwanted situations. Also adopting the right method of using hand sanitisers (with 70% alcohol) is required.”

There is another vital issue and that is pertaining to the ventilation system. It has become crucial to use adequate filtration before allowing outside air to come into a room. Similarly, ventilation is an important part to remove the exhaled virus-laden air from a room. Few organisations that are popular for dealing with building environmental control systems, namely REHVA (the European Heating, Ventilation and Air Conditioning Associations) and the American Society of Heating, Ventilating, and Air-Conditioning Engineers (ASHRAE) have also cautioned about the potential airborne threat indoors. These organisations have recommended scientifically established ventilation control measures to combat the virus.

Measures

Dr. Bhowmick told BE, “The risk intensifies when an air-conditioning system recirculate the air - as it lets the air to be distributed within the place easily. It can infect other people who will inhale polluted air - laden with the virus. In Peerless Hospitals, Kolkata, we have avoided that and established negated pressure wards where the Covid positive patients are staying. This will restrict the polluted air from coming outside - lowering the chance of further transmission. Then we allow the air to pass after proper air-cleaning.” Air-cleaning devices, particulate filters and disinfection equipment like Germicidal Ultraviolet (GUV) or Ultraviolet Germicidal Irradiation (UVGI) are also being recommended.

Physical distancing is important in every indoor office place. At the same time, reducing the number of workers is also necessary. Ionisation, bi-polar ionisation, Photo-catalytic Oxidation (PCO), Electrostatic Precipitator (ESP) and ozone generator are some of the major technologies to clean room air. Passive technology like HEPA filtration can also remove unwanted air particles down to 0.1 micrometres. 

A report titled ‘Covid-19 Guidance Document for Air Conditioning and Ventilation’ by The Indian Society of Heating, Refrigerating and Air Conditioning Engineers (ISHRAE) stated, “It is advisable to provide a Minimum Efficiency Reporting Value (MERV) 13 or higher filter fitted on the air handling unit. If fresh air is not provided, it is advisable to introduce a fresh air duct attached to a central inline fan filter unit and distribute the fresh air by grilles into the space or near the indoor units.”

Advisory by the Indian government

The Indian government has published various guidelines. In a recent advisory, it has stated, “Resident Welfare Associations functioning in gated complexes can play an active role in creating awareness about the Covid-19 disease by focusing on simple preventive measures that need to be followed.”

The advisory also stated,  “For air-conditioning/ventilation of common areas, the guidelines of the Central Public Works Department (CPWD) shall be followed which inter alia emphasises that the temperature setting of all air conditioning devices should be in the range of 24-30 C, relative humidity should be in the range of 40- 70%, recirculation of air to be avoided to the extent possible, intake of fresh air should be as much as possible and cross ventilation should be adequate.”

In a different advisory titled ‘Covid-19: Guidelines on disinfection of common public places including offices’, it has been informed by the government, “70% alcohol can be used to wipe down surfaces where the use of bleach is not suitable. Chloroxylenol (4.5-5.5%)/ Benzalkonium Chloride or any other disinfectants found to be effective against coronavirus may be used as per manufacturer’s instructions. Always use freshly prepared 1% sodium hypochlorite.”