ISHRAE issues guidance document for AC and ventilation for healthcare facilities

To draft the guidelines, a COVID-19 Task Force was set up by ISHRAE’s technical committee

The Indian Society of Heating, Refrigerating and Air Conditioning Engineers, Guidelines, COVID - 19, Vishal Kapur, AC and ventilation


The Indian Society of Heating, Refrigerating and Air Conditioning Engineers (ISHRAE) has launched a guidance document for AC and ventilation for residence, work space and healthcare facilities.  To draft the guidelines, a COVID-19 Task Force was set up by ISHRAE’s technical committee. It recommends that all facilities operated with AC and ventilation follow the guidelines.


Vishal Kapur, Chair – COVID 19 Task Force & ISHRAE Technical Committee states in the forward, “In preparing this document , the COVID-19 Task Force has extracted,examined, analysed and compiled information pertaining to the Climatic regions of the Indian Sub Continent. The Team referred to publications in peer reviewed journals and reports from other relevant organizations around the world in arriving at this conclusive guideline. The COVID-19 Task Force comprises members from academia, designers, manufacturers , service providers and subject matter experts of related sciences such as Filtration, Healthcare Facility design, Indoor Air Quality, Safety, Thermal Comfort , System Design and Operation & Maintenance.”

Regarding healthcare facilities,  the guidelines touch upon topics such as converting general patient rooms or ICUs into COVID-19 patient areas, treatment of exhaust air from COVID-19 patient areas, setting up make-shift isolation enclosures as well as quarantine areas. It also mentions about precautions to be taken at hospitals & laboratories.

Below is an extract from the guidelines for healthcare facilities:
Converting general patient rooms or ICUs into covid-19 patient areas – Considerations pertaining to HVAC systems:
COVID-19 positive patients and patients with COVID-19 related symptoms are to be accommodated in designated “Airborne Infection Isolation Rooms” in hospitals to control spread of the disease. However due to the surge in the number of such patients, healthcare facilities may not have adequate number of “AII” rooms to accommodate all such patients. Hence, healthcare facilities would need to convert their existing patient rooms or ICUs into COVID-19 patient rooms or COVID-19 ICUs to handle the current pandemic. The most important factor in this scenario is to ensure that the virus laden airborne particles do not leak out of the rooms occupied by COVID-19 patients and also to maintain the concentration of virus laden particles inside the COVID-19 patient room at a minimum. This is required to control the spread of infections and also to protect the healthcare workers.


As it is in normal practice, most of these patient rooms would be served by a HVAC system that would be of a recirculatory type, wherein the air from the room is taken back to the AHU for thermal conditioning and brought back. The same HVAC system could also be connected to a few other areas of the hospital. In some cases, there might be no dedicated return air duct and it could be a ceiling return system. If a COVID-19 patient had to be admitted to such a room, it would present a significant risk of the virus laden particles spreading out from the designated COVID-19 patient rooms.

To convert an existing patient room or ICU into a COVID-19 patient area, it is first necessary to convert the room into a non-recirculatory system (100% once through system) [11, 12]. On an emergency basis, this can be achieved by blanking (blocking) off the return air vents in the COVID-19 patient room. It is important to make sure that the AHU will have provision to receive adequate outdoor air supply. The outdoor air source for the AHU shall not be from within the building and all care shall be taken to avoid intake of outdoor contaminants, to the best possible extent. Additionally, an independent exhaust blower shall be provided to extract the room air and exhaust out into the atmosphere, preferably, after suitable “exhaust air treatment”. The exhaust air quantity shall be greater than the supply air quantity such that a negative pressure of minimum 2.5Pa (preferably >5 Pa) is achieved in the room . It is advisable to install differential pressure meters to measure this metric. The supply air quantity shall be such that it will provide a minimum of 12 air changes per hour. The position of the extract air in the room shall be just above the head of the patient's bed.

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