As we all know summer season is here and the weather is quite warm (some places are even hot). Now, what is the first thing we all think when we hear the word summer???
Yes, you are absolutely right!!!
AC i.e. air conditioner, or Cooler i.e. evaporative cooler generally called desert cooler.
Comfort is the topmost priority of the building occupant; health & performance is also dependent on the comfort perception of individuals. Generally, comfort temperature is between 22-32°C & comfortable relative humidity is between 45-65% in India during the summer season. People show adaptive behavior throughout India and their body accepts gradual changes and modifies themselves according to the current conditions. India is divided into 5 climatic zones which makes the range even wider when considering India as a whole for general comfort studies.
COVID-19 is at its peak in India and it is reported in many guidelines & reports that temperature and relative humidity affects the infection/ contamination rate severely. Many organizations are working on creating guidelines and codes on how to utilize ACs in the current situation without increasing infection cases in different types of buildings, especially in moderate, high, and ultimate risk buildings. However, Residential & Standalone office buildings are in a low-risk category but people are residing approximately 90-100% of their time in the current (lockdown situation). This makes us consider them equally important as other buildings.
Follow the below mentioned 5 key points to ensure minimum contamination/ infection risk in buildings.
1. Room Temperature
High temperature & high humidity significantly reduces the transmission of virus. SARS-CoV-2 has been found highly stable on surfaces for 14 days at 4 °C; one day at 37 °C and 30 minutes at 56 °C were needed to inactivate the virus. Considering comfort conditions with safety requirements, set room temperature between 24°C - 30°C (optimum comfort temperature according to SP41 – 27.5°C).
In Humid climate set temperature near to 24°C for de-humidification.
In Dry climate set temperature near to 30°C and use Fans for air movement.
2. Relative Humidity
Low humidity increases the infectivity of bacteria. 40% RH is considered the threshold. 80% and above RH tends to neutralize COVID-19 virus but this will increase dust mites and fungi which results in respiratory disease like Asthma. Considering all aspects of RH, 40-70% relative humidity is considered most suitable for comfort and safety.
In Dry climate if RH is below 40%, then put water filled pan for increasing indoor humidity by evaporating water.
3. Fresh Air Circulation
Fresh air circulation is quite necessary for health and comfort as human exhale carbon dioxide in the surrounding environment which increases the CO2 concentration indoors. Improper Air Movement can create high risk amid COVID-19 as it is spreading through air and can retain in air for hours. Maintain proper Circulation of fresh air by using Ceiling fan & slightly open doors and or windows and or exhaust fan.
Fresh Air must be ensured. Minimum fresh air volume of 3 cum/hour per person & 3.75 cum per hour per sqm (5 cfm per person and 0.6 cfm per sq ft) is recommended. If your building is mechanically ventilated then maintain minimum Air Exchange of: 10-15 ACHP, 70-80% fresh air circulation through mechanical ventilation must be ensured. Exhaust air quantity shall be greater than the supply air quantity.
Regularly discharge stale air by blowing air out frequently from your house.
4. Kitchen & Toilet Exhaust
Try to maintain good hygiene in kitchen & toilet. Kitchen & Toilet exhaust fans kept operational maximum time for better indoor hygiene and less respiratory problems.
At least switch on exhaust fan 15 minutes before & switch off 15 minutes after using them.
5. Indoor Sanitization & Cleaning
Frequent cleaning and sanitization of filters of indoor unit. Sanitize filters and other devices along with occupied space frequently for maximum safety.
Use World Health Organization (WHO) recommended standard disinfectant only for this purpose.
Hope this helps you and you will practically follow the guidelines and stay safe at your residences. For detailed guidelines please refer the references provided below. Do you have any other points in mind? Do let me know through available channels. All the Best!!!
“Knowledge is of no value unless you put it into practice.” – Anton C.
 “ASHRAE Position Document on Infectious Aerosols”, American Society of Heating, Refrigeration and Air-Conditioning Engineers, April 13, 2020.
 “REHVA COVID-19 guidance Document”, Representatives of European Heating and Ventilation Associations, April 3, 2020.
 “ISHRAE COVID-19 Guidance Document for Air Conditioning and Ventilation”, Indian Society of Heating, Refrigerating and Air Conditioning Engineers, April 13, 2020.
 “Guidelines for Running of Air Circulation, Air Cooling and Air Conditioning Equipments during Covid-19”, Central Public Works Department, Government of India, May 13, 2020
 “Optimize Occupant Health, Building Energy Performance and Revenue through Indoor-Air Hydration [Video recording]”, Stephanie Taylor (Presenter) Atlanta: ASHRAE, November 19, 2019.
 “Stability of SARS-CoV-2 in different environmental conditions”, A Chin, JTS Chu, MRA Perera, KPY Hui, et al., The Lancet Microbe 2020, Vol 5247, No. 20, p. 2020.03.15.20036673, 2020.
 “Collecting, preserving and shipping specimens for the diagnosis of avian influenza A(H5N1) virus infection : guide for field operations”, Geneva: World Health Organization, 2006.
 “COVID 19: Guidelines on disinfection of common public places including offices”, Ministry of Health & Family Welfare, Government of India, April 10, 2020.