Our aim in writing this article was to produce a 'laypersons guide' to workplace air quality, to identify some of the things that affect it and to provide some practical ways to help minimise Covid -19 risk.
Usually there will be a Nominated Person with responsibility for the maintenance and establishment of safe systems of work and safe working procedures with respect to air flows within their building(s).
Whoever this is should have basic knowledge and understanding of key issues including:
COVID -19 basic facts
The main risk for COVID-19 transmission is from a-symptomatic or pre-symptomatic people who are in your building without knowledge that they are shedding viral particles.
The SARS-CoV-2 virus which causes COVID-19 can be spread by very small particles – called aerosols – which are released by an infected person when they cough, sneeze, talk and breathe, alongside the larger droplets that are released.
The larger droplets fall by gravity, hence social distancing measures to reduce their spread. The fine aerosols, however, can remain airborne for several hours.
Droplet transmission (large droplets)
Airborne transmission (fine aerosols)
Coughs & sneezes can spread droplets of saliva & mucus.
Tiny particles, possibly produced by talking, are suspended in the air for longer & travel further.
Evidence gained from airborne aerosol transmission shows high rates of infection in poorly ventilated rooms - a potential transmission route.
These aerosols are at the highest concentration in exhaled puff and the idea behind social distancing was to help reduce exposure.
Aerosols that are small enough to remain airborne become diluted in the indoor air and without suitable ventilation they can build up, increasing the risk of exposure for susceptible individuals.
Risk is a function of exposure and duration exposed.
The risk of airborne infection to an individual can therefore be reduced by:
The ventilation rate and how it is delivered influences both airborne exposure and deposition rate (i.e., how much of the virus settles internally within the body).
Why ventilation is important for air quality
Ventilation is important as it can help to minimise the build-up of aerosols in a space and effective ventilation will reduce exposure risk. To achieve a good ventilation flow, you need to:
There are three basic approaches that you can adopt either individually or in combination to improve overall ventilation.
It is important to remember that ventilation needs to be considered alongside other controls to reduce the risk of transmission, such as social distancing, keeping a workplace clean and everyone adopting frequent handwashing.
You will need to make a Risk Assessment of the air quality within your workplace, most notably:
- Assess the risk from aerosol transmission in enclosed areas.
- Identify any poorly ventilated areas.
- Decide the steps you can take to improve overall ventilation.
Your priority should be to identify areas that are usually occupied but are also poorly ventilated. You should prioritise those areas, taking action to reduce the risk from aerosol transmission.
What do 'specialist building engineers' currently say about Covid-19 and air quality?
Next time: COVID – 19, Sick Building Syndrome, the effects of Ozone, VOC’s, Carbon Monoxide, Carbon Dioxide and Radon gas.
In our next article we will consider other air quality related health issues such as COVID – 19, Sick Building Syndrome, the effects of Ozone, VOC’s, Carbon Monoxide, Carbon Dioxide and Radon gas affecting air quality.