As building occupancy levels decreased in response to lockdown measures, the risk of legionella bacteria proliferation within water systems is likely to have increased. Whilst these should have been maintained and normal usage simulated as much as reasonably practicable throughout the lockdown, the risk of Legionnaires Disease should be considered prior to re-occupation of the buildings.
Before occupants start to return, occupiers must review their current legionella risk assessment. If this has passed its scheduled review date or has not been completed previously, then one should be completed as soon as possible.
A building is likely to be safe if, during lockdown, the following maintenance occurred:
If a building’s water services have not been maintained during lockdown, or the building has legionella positives either pre or during lockdown, then extra precautions should be considered:
Repeat chemical disinfections may be required in buildings with water services that have not been maintained during lockdown as biofilms within the water services may have developed which can shield bacteria from the disinfection chemicals.
Microbiological sampling should be undertaken to identify if there is still a risk associated with the building’s water systems and to prove the effectiveness of actions taken during lockdown. Samples should be taken at least 2-7days after any chemical or thermal disinfection. Reassurance samples should also be taken 2-4 weeks later to ensure that the controls put in place to reopen have been effective. Occupancy levels are likely to fluctuate in offices for several months so ensuring a thorough legionella prevention regime is in place is a priority.
David Coulston
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