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The Management of Mothballed / Low Occupancy Buildings during the COVID-19 Emergency Period

Management and Control of Legionella

Duty holders must continue to take reasonably practicable steps to control the risk of Legionella throughout the duration of the COVID-Legionella19 emergency period.  There is potential for a significant number of Legionnaires’ disease outbreaks following the COVID-19 pandemic if duty holders fail to effectively manage evaporative cooling systems; hot and cold water systems and other risk systems.When buildings become low in occupancy, or temporarily closed (mothballed), the potential for Legionella bacteria proliferation in water systems increases significantly; particularly during warmer months of the year.


EVAPORATIVE COOLING SYSTEMS: There is an expectation that evaporative cooling systems will be operated and maintained as normal, or else decommissioned safely in accordance with the site-specific written control scheme.  All evaporative cooling systems should already have robust start-up and shut-down procedures in place.

LOW OCCUPANCY BUILDINGS:  Where buildings are either empty or at lower occupancy levels, the site-specific risk assessment must be reviewed to identify what additional control measures need to be taken to address the issue of water stagnation.  Flushing of the system must continue, but should now include all other outlets that are infrequently used.  The frequency of flushing may also have to be increased to promote water turnover.  Where practicable, water levels in tanks should be reduced to minimise the amount of water storage.  Water temperatures still need to be maintained and monitored wherever possible; however, if this is not fully achievable due to access difficulties, the assessment must identify how the risk of exposure to contaminated aerosol is to be adequately controlled.

MOTHBALLED BUILDINGS:  HSG274 (Part 2) Paragraphs 2.50-2.52 should be followed.  In general systems should not be drained down and all sources of heat should be removed.  Water systems must not be put back into use unless an appropriate recommissioning process has been followed. Recommissioning work may include:

  • Flushing through simple hot and cold water systems with fresh mains water;
  • For larger building systems incorporating tanks, showers and calorifiers, more extensive flushing followed by cleaning and disinfection;
  • Where cleaning and disinfection is undertaken, monitoring the decrease in disinfectant level over the duration of the contact time (a reduction >40% could be an indication of biofilm in the system);
  • An increase in bacteria levels and biofilm is more likely during warmer weather conditions.  Disinfection of the system for an hour at 50ppm chlorine is advised in such circumstances.
  • After the system has been recommissioned it is good practice to evidence that the process has been effective.  Sampling to BS7592 should be considered, with samples taken 2-7 days after the recommissioning process.

Further information available at: ACoP L8 (4th Edition; 2013) – Legionnaires’ Disease: The Control of Legionella Bacteria in Water SystemsHSG 274 parts 1-3  – The Control of Legionella Bacteria in Evaporative Cooling Systems; Hot and Cold Water Systems; In Other Risk Systems.Acknowledgment to both Vector Air & Water and the Legionella Control Association for the information produced in this document.

Statutory Thorough Examination & Testing of Plant and Equipment

During the Coronavirus Pandemic duty holders may experience difficulties meeting their statutory obligations to complete statutory thorough examination and testing (TE&T) of plant and equipment under the Lifting Operations and Lifting Equipment Regulations (LOLER) and the Pressure Systems Safety Regulations (PSSR).  This may be due to a reduced availability of engineers; engineer refusal to access premises; plant and equipment being unavailable for testing due to buildings being closed or building owners refusing access to engineers.The statutory obligations remain in place and duty holders must adopt a risk-based approach when all attempts to arrange TE&T have been unsuccessful.

Duty holders must make reasonable efforts to arrange for TE&T to be undertaken within the statutory time limits:

  • Make appointments with engineers in good time to ensure TE&T within statutory limits.
  • Source engineers from another provider where usual inspection body is unavailable.
  • Facilitate engineer access to equipment (e.g. if building closed).
  • Ensure social distancing measures can be achieved whilst engineer on site.
  • Make reasonable efforts to make hygiene provisions available for hand washing.
  • Make reasonable efforts to ensure surfaces are cleaned / disinfected afterwards.

Where duty holders are unable to arrange TE&T within the statutory limit, competent advice must be sought from their inspection body to determine if plant/equipment can continue to be used safely outside of the statutory regime.  If plant/equipment cannot continue to be used safely, it must be taken out of use.If plant/equipment can continue to be used safely outside of its statutory testing period, the duty holder must document:Efforts made to get plant/equipment tested Decision making process followed and factors considered when reaching this decision.Additional measures identified to minimise any potential risks arising from continued use. Introducing robust inspection or extra maintenance by competent persons during the interim period.

Further information is available at: 

Reporting of Injuries, Disease and Dangerous Occurrences Regulations 2013

  • Dangerous Occurrence – an unintended incident at work which has led to someone’s possible or actual exposure to Coronavirus.
  • Occupational Disease – a worker has been diagnosed as having COVID-19 and there is reasonable evidence that it was caused by exposure at work.
  • Fatality – worker dies as a result of exposure to Coronavirus.

COVID-19: Cleaning in Non-Healthcare Settings 

Where a symptomatic individual has been in the work place, an enhanced cleaning and disinfection protocol must be followed.

  • As a minimum, good fitting disposable gloves and a disposable apron should be worn.  Your risk assessment should identify the need for any additional PPE.
  • All surfaces that a symptomatic person has been in contact with must be cleaned and disinfected.• Disposable cloths; paper towel and disposable mop heads must be used.
  • Either use a detergent disinfectant at a dilution of 1000 parts per million (ppm) available chlorine, OR use a detergent to pre-clean surfaces before disinfecting with a product diluted to 1000 ppm available chlorine, OR use a detergent to pre-clean surfaces before disinfecting with a product that is effective against enveloped viruses (check manufacturer’s guidance to confirm this).
  • Apply all disinfectants for the contact time prescribed by the manufacturer for the dilution being used.• When items cannot be cleaned with a chlorine based product (or equivalent), steam cleaning may be carried out.• All contaminated waste (PPE, cloths, aprons, tissues etc.) must be double bagged, secured and marked for storage for at least 72 hours, or until any test results of the individual are known.
  • Thoroughly wash hands for at least 20 seconds with warm water and liquid soap after PPE has been removed and cleaning tasks completed.  Ensure hands are hygienically dried.

Further information is available at: