Airflow in Supermarkets and Similar Retail Stores: a rapid survey on infection transmission

Abstract

Purpose: to assess the literature relating to ventilation in supermarkets and similar retail premises and whether or how to alter ventilation (HVAC system) operation to minimise the risk of cross-infection in the light of the size of aerosols exhaled by customers from normal activity. Objectives: 1) ascertain the typical size range of particles and droplets exhaled; 2) examine current system design and operation guidelines; 3) report on advice from professional bodies about feasible changes to current practice. Summary: 1) Breathing expels a wide range of droplet sizes with some studies showing 80– 90% of particles are smaller than 1 μm (non-settling particles). 2) Typical HVAC configuration gives a well-mixed air flow through most of a store. 3) Air flow rates in supermarkets are large compared with exhalation volumes from customers; exhaled non-settling particles will be carried in the airflow. 4) Increased air changes per hour further reduces the risk of cross-infection. Assumptions: 1) UK stores of mainstream food and other retailers. 2) Customers are not displaying obvious symptoms of SARS-Cov2 (i.e. not coughing) as they are already instructed to self-isolate. Customers are either free from the virus or are asymptomatic. 3) People breathe normally and speak at normal conversation levels.