ASHRAE Journal - July 2021 - 14

TECHNICAL FEATURE
Analysis of Spread of
Airborne Contaminants
And Risk Of Infection
BY KISHOR KHANKARI, PH.D., FELLOW ASHRAE
As businesses are poised to reopen amid the COVID-19 pandemic, people are looking
for comprehensive guidance for proper ventilation of indoor spaces. Computational
fl uid dynamics (CFD) was used to study the impact of the HVAC layout (location
and number of supply diffusers and return grilles) on indoor airfl ow patterns and
the resulting risk of infection. The results indicate an HVAC layout with distributed
supply and distributed return can form an aerodynamic containment (airfl ow envelope)
that can help reduce the spread of airborne contaminants and reduce the risk
of infection without increasing the supply airfl ow rates. CFD analyses, if performed
properly with adequate expertise, can help professionals understand complex airfl ow
patterns and the fl ow path of airborne contaminants.
Airfl ow, Ventilation and CFD
Air can carry small droplets and particles containing
the SARS-CoV-2 virus that causes COVID-19 over a long
distance. Depending on the local airfl ow patterns, some
of these respiratory droplets can travel much farther
than 6 ft (1.8 m).1 Often good ventilation is recommended,
along with social distancing and face-covering
measures to control the spread of the SARS-CoV-2
virus.2
Good ventilation is commonly referred to and understood
as an increased supply of clean air or increased
air change rates per hour (ach, h-1) for enclosed spaces.2
However, simply increasing the supply of clean air
may not be suffi cient to achieve good ventilation.2,3
Increased supply airfl ow rates can help in the dilution
of airborne contaminants and reduce the overall
concentration levels. However, the increased supply
airfl ow rate may not necessarily ensure the acceptable
concentration levels everywhere in the occupied zone.
High concentration, especially in the breathing zone,
can pose a potentially higher risk of infection.4 Airfl ow
patterns and resulting distribution of clean air in indoor
Kishor Khankari, Ph.D., is the president at AnSight LLC in Ann Arbor, Mich.
This peer-reviewed article does not represent offi cial ASHRAE guidance. For more information on ASHRAE resources on COVID-19, visit ashrae.org/COVID19.
14
ASHRAE JOURNAL ashrae.org J U LY 2 0 2 1

http://www.ashrae.org/COVID19 http://www.ashrae.org

ASHRAE Journal - July 2021

Table of Contents for the Digital Edition of ASHRAE Journal - July 2021

Contents
ASHRAE Journal - July 2021 - Intro
ASHRAE Journal - July 2021 - Cover1
ASHRAE Journal - July 2021 - Cover2
ASHRAE Journal - July 2021 - 1
ASHRAE Journal - July 2021 - Contents
ASHRAE Journal - July 2021 - 3
ASHRAE Journal - July 2021 - 4
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ASHRAE Journal - July 2021 - Cover3
ASHRAE Journal - July 2021 - Cover4
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