Re-opening offices - legionella risks emerging from lockdown

The COVID-19 pandemic led to the closure of offices and resulted in millions of people having to work from home, with employers deploying their attention and energy to ensuring the safety of their workforce, whilst also striving to maintain their businesses.

During the first lockdown, certain measures were taken so that if or when workers returned to their offices, they would find them to be ‘COVID-secure’. Shift rotations, one-way systems, hand sanitiser stations, warning notices and signing-in registers are now all commonplace to those who have ventured into their offices. But what about other risks, such as the risk of exposure to legionella bacteria? This is a real and very dangerous risk, particularly given that many work premises have been empty for so long.

With vaccine rollouts now under full swing, many parts of the world, including the UK, are preparing to reopen. Businesses should now be shifting their focus to developing a strategy for the re-start of operations to include identifying and managing risks associated with legionnaires’ disease in buildings that were closed or had reduced occupancy during the lockdown period.

What is legionnaires’ disease?

Legionnaires’ disease is a potentially fatal form of pneumonia caused by the release of droplets containing legionella bacteria. The bacteria is commonly found in natural water sources but also in purpose-built water systems, such as cooling towers or hot and cold water systems.

In an office environment, contraction of the disease is possible where the bacteria has grown in parts of the water system where temperatures range between 20 and 24 degrees Celsius. Droplets containing the bacteria may be released from water systems which can result in contraction of the disease when inhaled.

As with coronavirus, there are some who are at higher risk including those over 45 years old, smokers and heavy drinkers, people already suffering with existing kidney, lung or chest disease and those with an impaired immune system.

Symptoms include a high temperature, cough, muscle pains, headache and difficulty breathing. Legionnaires’ disease is not transmissible from person to person and is treated by antibiotics.

What are an employer’s duties in relation to legionella?

The Health and Safety Executive (HSE) has issued guidance and advice to employers and those in control of buildings, reminding them of their legal obligations to protect employees and visitors against the risks of legionella.

All employers and building controllers should have a risk assessment relating to legionella and must review that assessment and take steps to prevent the growth of the harmful bacteria. Where there are hot and cold water systems, these will need to have been flushed through on a weekly basis to prevent the water stagnating and bacteria cultivating. Where this has not happened, it is imperative that contractors are engaged to clean and, if necessary, disinfect the water systems. Records need to be updated as evidence of the steps taken to show statutory compliance.

In larger shared buildings, it is incumbent on landlords to understand the extent of their duties and ensure that compliance is adopted throughout a building. Risk will still exist where only parts of multi-occupancy buildings adopt statutory compliance, as this still enables harmful bacteria to grow in water systems and droplets to escape into working environments.

Should duty holders fail to take action and manage the risks associated with legionnaires’ disease, they could be found in breach of health and safety law and as such, find themselves subject to fines, enforcement notices and even criminal prosecution.


There appears to be an end in sight to the draconian measures that have been in place over the past 12 months. In unlocking offices and allowing employees back into work, employers and landlords must assess the risk relating to legionnaires’ disease, and ensure that all steps are taken to facilitate a safe office working environment.

Read other items in Occupational Disease Brief - April 2021

Related content