How do I mitigate the risk of contamination in washrooms?

There are 3 main scenarios for contamination i.e.:

  • Contact: This may occur direct from person to person, or indirectly via person to surface to person
  • Airborne: Large droplets (>10 μm) are expelled by sneezing and coughing, and in still air typically drop within about 2 m of the infected person. Small droplets (<5 μm) may travel for long distances
  • Faecal–oral: Maintaining water in toilet traps and making sure that toilet lids are closed before flushing is important.

Covid-19 can be spread through the intake of contaminated water droplets which are generated in two ways namely oral aerosol (e.g. coughing, sneezing) and faecal aerosol (e.g. sewers, flushing of toilets following use by an infected person). As washrooms are areas that will remain in frequent use once reocupation of offices occurs, it is recommended as part of the re-entry policy that face coverings are required and physical distancing rules are adhered to as appropriate using the same methodology as the office plan (marking of areas in and out of use, appropriate signage, directional arrows etc.).

Washroom and building systems recommendations

Recommendations specifically for washroom areas and building systems include the following:

  • Supply as many ‘air changes’ as possible to occupied spaces
  • Maximise the fresh air volume
  • Run the fresh air system 24/7
  • Check operation of toilet extract systems and run them 24/7 ensuring that a negative pressure is maintained in toilet cubicles to minimise faecal–oral transmission. Included signage to close the lid of the WC before flushing
  • Switch fan coil units off or operate them 24/7
  • Fresh air systems that use rotary heat exchanges and/or enthalpy wheels may carry over Covid-19 particles from the return air to the supply air so it is important to shut down the enthalphy or thermal wheels from turning
  • If there is a suspected leakage in the heat recovery sections of fresh air systems these should be reconfigured so that the supply air runs at a higher pressure than the return air side and/or physically block the leakage

Stop or prevent recirculation of air. However, for displacement air and VAV systems this will be an issue as these systems are likely to be running on 60-80% recirculated air. Therefore consideration should be given to:

  • Only running these systems out of hours
  • ‘spilling’ the return air and operating these systems on 100% fresh air


  • For 100% fresh air systems no action is required
  • Most systems have the primary filtration on the incoming outside air so for Covid-19 contamination this is unlikely to be the source
  • Most AHU primary filtration removes particles of between 1-3 Micros in size, with HEPA filters capable of removing down to circa 0.3 Micros
  • Although C-19 is circa 0.1 Micros in size its ‘droplet vehicle’ is likely to be 2-5 Microns so a return air primary filter bank will be helpful in reducing the transmission
  • Check the rating of filters and IF return air filters are fitted

Ultraviolet Germicidal Irradiation (UVGI) can be retrofitted to a ventilation system and /or air handling units. UV sterilisation:

  • Uses UVC light (certain spectrum of UV light) and is effective in controlling bacteria, fungal growth and viruses
  • Is relatively common in AHU’s to control ‘bio-films’ on cooling coils
  • Has a negligible increase in system pressure
  • Can be designed as a single pass high efficiencies installation.

Other measures that can be brought in:

  • Regularly water ‘wet traps’ to inspect and maintain the seals
  • Introduce copper as a antimicrobial surface coating on touch-point surfaces (e.g. door handles, push plates)
  • Regular duct cleaning / sterilisation (although virus particles will not deposit readily in ventilation ducts and will normally be carried on by the airflow)
  • Introduce santisation stations at entrance/exit point of washrooms
  • Incorporate touchless technologies where possible
  • Consider occupancy solutions such as: apps; traffic light systems; and sensors to inform building users when washrooms are full and to queue outside, a simple red / green ticketing solution can work but would not provide the touchless solutions available through technology.

People who are shielding have extra protections

Many will be disabled for the purposes of the Equality Act 2010 and insisting they come back to work may be unlawful as it could be classed as discrimination arising from disability or failure to make reasonable adjustments. To be protected disabled people must have a physical or mental impairment which has a substantial and adverse effect on ability to carry out day to day activities. Certain health conditions, such as cancer and multiple sclerosis are automatically treated as disabilities. There may also be age discrimination issues.

Those people who are shielding are also be protected from detriment or dismissal for a health and safety reason under the Employment Rights Act. If an employer insists on a return to the workplace this may be a constructive unfair dismissal which could be automatically with no minimum qualifying period of employment being required to bring the claim.

All employees (not just those who are shielding) who reasonably believe themselves to be in serious and imminent danger are entitled to take appropriate steps to protect themselves.

If there are aspects of work that can be done from home, this is likely to be a reasonable adjustment which must be considered for those who qualify under the Equality Act disability provisions. Requests to continue home working are likely to fall within the requests for flexible working legislation.

Living with people who may be shielding

The protections referred to above are also likely to protect employees who live with people who are shielding. The Equality Act 2010 protects people from discrimination as a result of their association with a disabled person. Employers who give a blanket refusal to consider continued working from home would disproportionately impact people who are associated with disabled people. It is also likely that they have protection from detriment or dismissal as there are genuine health and safety reasons for needing to stay away from the workplace. As ever, each case needs to be looked at on its own facts. Employees are also entitled to reasonable time off to provide assistance for dependents who are ill. If the person shielding is a child parental leave of up to 18 weeks may also apply. Shielding employees with underlying health conditions employers can seek the support of occupational health or other professionals for risk assessments, and advice on returning to work or on reasonable adjustments. The risk for shielding employees are not simply those in the workplace, but also the exposure in their commute to work and back. Employers should be flexible and understanding and keep the health and safety of their employees as their priority.


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Home working

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For more advice on reopening your workplace, navigate left and right through this resource centre and read our Q&A document.

This webinar and Q&A document reflects our professional opinion of the factors impacting workplace transition in the context of our role as workplace specialists. It does not constitute formal advice and we recommend engagement with specialists, including your own internal or external health and safety advisors, if you are transitioning your workplace to a 'Covid secure' standard. Please also note that the Q&A contains responses to specific questions which therefore may not be appropriate for all types of businesses or workspaces. The spread of COVID-19 and the containment policies being introduced are changing rapidly, and some of the views expressed herein may not reflect the latest opinion of Avison Young. We strongly recommend that you continue to monitor the relevant UK Government advice, and any supplementary local advice. These sources provide regularly updated information on the COVID-19 outbreak: World Health Organization, Government of Canada, U.S. Centers for Disease Control and Prevention, UK Government, Johns Hopkins University COVID-19 Case Tracker.