Covid-19: Human Resources Ministry releases Health and Safety Guidance Notes on Ventilation and Indoor Air Quality

21 July 2021

1. the recommended indoor thermal conditions are between 23°C to 26°C and 40% to 70% relative humidity with clean filtered air;
2. electric/ceiling fans should be used to increase air circulation;
3. air-conditioners should be operated as recommended in (a) and (b) above with a small window opening left open barring any excessive infiltration of air;
4. when air-conditioners are not in use, the windows should be kept open to ventilate room spaces with clean outdoor air;
5. exhaust fans should be operated in bathrooms and/or common areas in low/high rise apartments;
6. the water seal in the sanitary system should remain intact and any cracks should be rectified;
7. for low/high rise apartments, the use of open windows adjacent to or close to neighbouring units should be minimised; whereas the use of balconies in close proximity with neighbouring units should be avoided, to reduce the risk of infection from one apartment unit to another; and
8. where a household member is ill, suspected or infected with the COVID-19 virus, an isolation space/room should be allocated without the use of air-conditioner but natural ventilation instead. The isolation space/room should have its own bathroom facilities to reduce the risk of infection to other household members.   

1. Centralised Air Conditioning System

• ensure all components and controls of the centralised MVAC system are maintained and functioning.
• outdoor fresh air ventilation should be increased to a minimum of 10L/s per person of fresh air. This may be carried out by opening outdoor air dampers to 100% to increase effective dilution ventilation per person;
• filters should be changed as per the recommended maintenance frequency whilst the filter seals should be checked to avoid bypass;
• occupancy density in air-conditioned spaces should be reduced. 
• the indoor temperature should be between 23°C to 26°C and relative humidity should be between 40% to 70%;
• the building’s water system should be flushed and maintained properly;
• usage of MERV 13 or higher MERV value filters should be considered in accordance with the capabilities of the MVAC systems; and
• if the restroom is located adjacent to an occupied space, the exhaust fan should run continuously to keep the negative pressure relative to the corridor or adjacent room.  

2. Non-Centralised Air Conditioning System

• windows and doors should be kept open frequently to allow cross natural ventilation and fresh air into the space, save for any poor outdoor air quality or weather. Where windows and doors are open, use of the air conditioning system should be kept at minimum or turned off completely;
• exhaust fans should be operated in bathrooms or kitchens at maximum capacity;
• use of portable air cleaners with particle filters of MERV 13 may be considered; and
• the water seal in the sanitary system should remain intact and any cracks should be rectified.

3. Naturally Ventilated Spaces

• windows and doors should be kept open frequently to allow cross natural ventilation and fresh air into the space, save for any poor outdoor air quality or weather;
• ventilation may be improved by purging the area frequently by opening all doors and windows completely especially when the area is not occupied;
• do not direct the airflow of the fan directly from one person to another person as it may increase the risk of airborne transmission; and
• if exhaust fans have been installed, the use of such fans should be considered to increase ventilation i.e. in bathrooms and/or kitchens.

1. Engineering Controls

• increasing the outside air ventilation;
• increasing the air filtration by inter alia upgrading MVAC filters to MERV 13 (or the highest MERV rating a building’s ventilation system can accommodate) and placing portable air cleaners at high density or occupancy areas; and
• adjusting or reconfiguring air flows by inter alia operating exhaust fans in restrooms to reduce the risk of indoor airborne transmission.

2. Administrative Controls

• implementing work practices designed to reduce crowding or occupancy such as telework, staggered schedules and remote/video meetings; and
• limiting the use of small spaces that are shared such as laundry rooms and lobbies.

3. Reconfiguration of Building Spaces and Furnishings

• the use of partitions to reduce the risks of transmission by minimising direct air flow between individuals in building spaces.

4. Cleaning and Disinfection

• where there has been a suspected or confirmed case of COVID-19, cleaning and disinfection should be carried out within 24 hours; 
• if more than 24 hours have lapsed since the suspected or confirmed case of COVID-19, cleaning would be sufficient unless there is, inter alia, high index transmission of infection in the area and the presence of individuals susceptible to COVID-19; and
• if more than three days have lapsed since a suspected or confirmed case of COVID-19, no additional cleaning other than the usual cleaning is required.

1. in relation to air-conditioned facilities with mechanical ventilation and air-conditioned facilities without fresh air supply, the use of high-efficiency filters (at least MERV14 or F8) is recommended in AHUs. Filters should be properly installed, regularly inspected, maintained, and cleaned according to manufacturers’ recommendations; and

2. although stand-alone air cleaners with appropriate filters may be used if no other (short term) strategy can be adopted, it is emphasised that the stand-alone air cleaners do not replace ventilation in any circumstance.