HVAC professionals must be diligent to ensure they minimise the risk of a Legionnaires’ disease outbreak on restarting any facility that has been partially or fully shutdown.

Legionella bacteria can proliferate in stagnant pipework and any relaxation of COVID-19 shutdown measures could increase the risk of a Legionnaires outbreak.

Australia’s coronavirus suppression strategies have successfully controlled the escalation of COVID-19 cases.

But the suppression measures led to the shutdown of many buildings including clubs, hotels, restaurants and sports facilities. In addition, many commercial facilities moved from full occupancy at the start of March to minimal occupancy for the past four to six weeks.

HydroChem  CEO, Nicholas Duncan, said ideally cooling water systems went into hibernation, with ongoing disinfection to minimise the risk of Legionella growth within pipework.

“If not, the managers of these facilities must take additional precautions when restarting cooling systems,” he said.

“Buildings that have been partially or fully shutdown for more than a week are likely to have stagnant water in the pipework that distributes water to taps, showers and ice machines. This water presents a risk of propagating Legionella.

“We also need to be especially mindful of people at a higher risk of contracting Legionnaires’ disease – such as people who are immunocompromised or have pre-existing health conditions.

“We recommend all water distribution systems are flushed before use and Legionella testing is conducted to identify any compromised systems.”

As buildings are reoccupied and pedestrian activity increases, Duncan said it is important that water systems are properly recommissioned and tested to mitigate the risk from Legionella that may have developed during the shut-down.

Legionnaire’s disease presents similar symptoms to COVID-19 such as fever, cough, shortness of breath and potentially fatal pneumonia.

Recommendations for cooling water systems:

Preferably, cooling water systems should be in “hibernation”, not shutdown

If not in hibernation, all pipework and equipment must be fully drained

Prior to start-up of any cooling water system, a cooling tower clean must be conducted and care must be taken to disinfect all system water

Recommendations for water distribution systems:

Prior to facilities being opened for use, all water outlets should be flushed for at least 3 minutes each

Legionella testing should be conducted to ensure pipework has not been colonised by Legionella during periods of stagnancy


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