Air conditioning systems are having a growing impact on the quality of air inside Australian homes and offices. And it’s not just about keeping the air cool. They also play a key role in managing all sorts of indoor pollutants like dust, dampness and noxious gases. How effective they actually are has become a lot clearer thanks to health-based guidelines, building regulations and research into the impact of indoor air quality on people’s health.
The Air Filtration Bit and Its Real-World Impact
When it comes to air quality inside Australian air conditioning systems, how good they are at filtering out tiny particles is one of the most important things to know. Most standard residential units use MERV 6 8 filters which can pick up particles 3 microns and bigger, although that only works for around 35 70% of particles. You can get better filters with MERV 11 13 which will pull out up to 85% of fine particles. Then there are the high range HEPA systems which can capture 99.97% of 0.3-micron particles in a lab. But the numbers only tell part of the story, especially when you see what the air inside a typical Australian home is really like. Without air filtration, the levels of nasty PM2.5 particles inside houses are often between 12 and 25 micrograms per cubic metre. That’s a long way off what the World Health Organisation says are safe levels of 5 micrograms. However, when air filtration kicks in, that exposure drops by 50 80% and the risk of people getting sick from breathing that in goes down too. And it’s not just about the filtration system, continuous air recirculation can also help lower dust levels by 40%. In fact, a recent study done in Melbourne by Gas Chill showed that if you fit a better filtration setup in a house, you can actually get the air inside to a level where it’s safe to breathe, of around 8 micrograms a cubic metre.
Keeping the Humidity in Check, The Unseen Action
As air conditioning systems go about their job, they’re also quietly controlling the humidity in the air. And that’s a big deal. Experts reckon that keeping the relative humidity inside between 40 and 60% is the sweet spot. Within that range, people tend to notice a big difference, especially when it comes to dust mites. In fact, research has shown that for every 10% you drop the humidity level, you can knock down dust mite populations by 20 25%. Which is pretty important in Australian cities like Brisbane and Sydney where the humidity outside can get pretty high, sometimes up to 80% in the summer. But if left unchecked that can lead to a host of other problems, like mould and fungal spores. Air conditioning can help here too, by reducing the amount of moisture in the air and cutting back on mould growth by up to 60%. In fact, studies have shown that damp houses are more likely to see asthma hospital admissions go up, by as much as 30 40%. On the other hand, regulated air conditioning can actually reduce airborne fungal spores by almost half.
Ventilation Dynamics and Indoor Pollutant Dilution
Air moving around in HVAC systems is also a big deal when it comes to controlling indoor air. We’re all familiar with the differences between commercial buildings and homes in Australia. In fact, the mechanical systems in most commercial buildings here typically do around 4 to 8 air changes per hour (I think of that as just a fancy way of saying air turnover), while homes that rely on natural ventilation are lucky to get 1 ACH. The difference this makes to indoor air quality is pretty striking. Volatile organic compounds, like benzene and formaldehyde, can actually be cut by 30 50% with a constant airflow going on. Plus, carbon dioxide levels get kept in check at a healthier 600 800 parts per million, rather than spiking up above 1000ppm and leading to a 15 20% hit to brain function. And when it comes to workplace studies that follow Australian standards, a properly maintained mechanical ventilation system is shown to cut the incidence of sick building syndrome by a quarter. One of the other big benefits of air exchange is that it greatly limits how long aerosols can hang around. Even in high efficiency systems, airborne pathogens can be cut by up to 60%. However, it’s worth noting that this is not always the case. If a system is poorly maintained it can actually lose efficiency, with some systems showing losses of up to 20%.
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