The Chartered Institution of Building Services Engineers (CIBSE) has published various documents addressing a number of issues that must be considered for the safe reoccupation of buildings.
CIBSE Covid Emerging from Lockdown: Safely Re-occupying Buildings is intended to give business owners and managers an outline of the main areas to be considered concerning both safe working practices and the assessment of building services.
The advice in CIBSE Covid Ventilation Guidance is for building owners/managers and operators when reopening buildings following a period of inactivity and considering the requirements for the ventilation system.
Many lifts and escalators will have been switched off for lockdown. Although most will go back into service without any glitches there are some precautionary steps that should be taken before returning them to regular service, looked at in the guide CIBSE Covid Recommissioning of Lifts and Escalators.
The documents can be found here.