Delivering Resilience: Evaluating public buildings to provide cleaner indoor air shelters

Learn how a data-driven case study in Port Macquarie tests how well a public building can reduce smoke exposure during bushfire events, helping address a key evidence gap in clean air shelter planning.

'During extreme air pollution events, such as bushfires, public health messaging recommends vulnerable groups stay indoors with the doors and windows closed or go to an air-conditioned building such as a library. However, smoke can still make its way inside, because many Australian buildings are relatively leaky allowing outdoor smoke to seep indoors'.

Kerryn Lawrence, Manager Environmental Health, Far West and Western NSW Public Health Unit

Exposure to bushfire-related smoke can have significant health impacts, including cardiac and respiratory issues, which may result in greater use of asthma reliever medication, increased emergency department visits and potentially deaths. Particulate matter (PM 2.5) is the component of smoke most strongly and consistently linked with adverse health effects. Around one-third of the Australian population is at elevated risk of developing smoke-associated illnesses during extreme smoke events.

The NSW and Australian Regional Climate Modelling (NARCliM 2.0) projects the number of severe fire weather days will increase for NSW by 2050 resulting in more frequent and intense smoke events.

The selection of the Port Macquarie library for assessment as a potential “cleaner indoor air shelter” was made after considering several public buildings. There are a range of factors that make the buildings suitable for this use, these include accessibility, presence of air-conditioning, access to WIFI, sufficient seating for the public, and access to public toilets, among other criteria. A local checklist tool was developed specifically for this occasion.

'We measured PM2.5 concentrations from August 2019 to November 2019 using Smoke Observation Gadgets, (SMOG) developed by CSIRO. Pairs of monitors were placed indoors in the main library and in the media room where the HEPA cleaners were located, and the outside library courtyard. To help validate the data quality and performance of the low-cost sensors, we placed another pair adjacent to a reference monitoring station in the town.'

Dr Amanda Wheeler, Principal Research Scientist, CSIRO

The library HVAC system used disposable cardboard pleated filters rated F5, Type 1, Class A that were replaced annually. The HVAC system operated from 8 a.m. to 7 p.m. with a 10% fresh air intake during operation. The library entrance consisted of two sets of automatic sliding doors, that could be opened at the same time. 

Two portable HEPA cleaners with Grade H12 HEPA filters were placed in the library’s media room and operated on a medium fan setting during the study.

Data was analysed separately for periods with and without the HEPA cleaners operating.

During the five‑month study, outdoor PM2.5 levels were above the national standard of 25 µg/m³ on 34 days, and on one of those days the level was about 24 times higher than the standard.

Indoor air quality in the main library was consistently better than outdoors, with outdoor-generated PM2.5 reduced by about 70%. Portable HEPA air cleaners operating in the media room provided additional protection, lowering PM2.5 by a further 17% compared to the main library.

These findings suggest that large public buildings with well-maintained central air conditioning can serve as effective cleaner indoor air shelters during smoke events, and that portable HEPA units can offer extra benefits in smaller spaces. 

A carefully selected central air-conditioned public building could be used as a cleaner indoor air shelter during prolonged smoke events. Further improvements in indoor air quality can be achieved by operating appropriately sized portable HEPA cleaners and adopting practices that restrict outside air infiltration during times of poor air quality.

As a starting point the building features to look for include:

• Presence of well-maintained air conditioning with filters and variable air exchange rate, and a user guide
• Control of external openings such as doors and windows
• Ease of public access, including disabled access, car parking and public transport
• Access to wifi and spaces for the public to sit
• Drinking water and public toilets

As climate change increases the frequency and severity of smoke episodes, integrating cleaner air spaces into building design and adaptation planning is a practical, scalable strategy to help protect public health. It is important that appropriate public buildings can be identified and properly managed to provide priority communities with relief during periods of poor air quality. Providing cleaner air spaces can also complement other programs such as providing refuge from excessive heat.

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