Infographic depicting sanitised air flowing through Air Handling System/AIr Handling Unit in Changi's terminals.

Clean indoor air is vital for infection control to mitigate the spread of viruses via airborne particles and droplets. The air-conditioning and mechanical ventilation systems in Changi’s terminals are installed with different layers of filters, namely the upgraded MERV-14 and Ultraviolet-C sanitisation equipment to sieve out pathogens of different sizes in the air flow passage. In more contained spaces where passengers and staff dwell, these areas are supplemented with air purifiers fitted with hospital-grade High-Efficiency Particulate Air (HEPA) filters.

Even before the pandemic, the ventilation systems in the airport’s passenger terminal buildings, which are designed with an airy ambience by having high ceilings and wide-open spaces, are calibrated to completely refresh the indoor air every six to ten minutes. For washrooms, the air change takes place even more frequently, every three minutes. This is more frequent than the recently updated national guidelines to improve building ventilation and indoor air quality. 

Take a look at the journey of air particles through Changi Airport’s air-conditioning and ventilation system.

Effective removal of coronavirus with upgraded Minimum Efficiency Reporting Values (MERV) filters

Since the onset of Covid-19, the air-conditioning system filters across the passenger terminals have been upgraded from MERV-7-rated models to MERV-14-rated ones. These higher grade filters can effectively remove about 85% of the particles in the air of 0.3 - 1.0 micrometres in size – smaller than the size of a coronavirus particle in respiratory droplet.

To ensure the MERV-14 rated filters continue to operate at effective efficiency, they are replaced every one to two months, depending on the condition of use. All used filters are sealed for proper disposal by maintenance workers donning highest level personal protective equipment for safe handling.

In addition, fresh air intake for the air-conditioning systems have also been maximised by fully opening the dampers to admit outdoor air.

Ultraviolet-C sanitisation kills remnant virus traces

As a further layer of protection, Changi Airport is installing Ultraviolet-C (UV-C) sanitisation equipment in Air-Handling Stations (AHS) and Air-Handling Units (AHU) progressively across all the terminals’ air-conditioning systems. The UV-C kills any remnant virus traces in the mixture of fresh and returned air passing through the cooling coil, providing a second level of defence after the MERV-14 rated filters. The first round of such installations will be completed this month at selected AHSs and AHUs which supply air to mission-critical control rooms and higher risk zones.  

Portable air purifiers with HEPA filters installed at more contained spaces to further clean the air

In more contained spaces, such as transfer holding areas, staff canteens and food courts, staff rest areas in the new segregated zones across the terminals and at heath scanning stations, portable air purifiers with hospital grade High-Efficiency Particulate Air (HEPA) filters have been installed. This is to further mitigate the risk of airborne transmission of the Covid-19 virus.

This increased protection means that after the air in the terminals has been scrubbed by the MERV-14 filters, the portable air purifiers with HEPA filters further cleans air distributed into the building interiors, removing more than 99% of any remaining particles. Depending on the air purifiers’ capacity, it takes just three minutes to clean the air in an area about the size of a two-room flat.

Low Carbon Dioxide Levels, High Indoor Air Quality

Changi Airport Group worked closely with health agencies and performed several smoke diffusion tests to ascertain that the design of the indoor air flow does not contribute to any adverse movement of air from higher risk to lower risk zones.  For quality assurance, CAG also conducts regular checks on indoor air quality, including measuring CO₂, air pollutants, humidity, temperature and flow rates.

With these multi-layers of protection in place, the Carbon Dioxide (CO₂) level in Changi Airports’ terminals remain constantly low, at less than 500 ppm (parts-per-million). This is nearly 30% better than the allowable CO₂ level stipulated in the Code of Practice for Indoor Air Quality.  Hence, visitors can be assured of good ventilation and higher quality indoor air every time they use Changi Airport.