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Buying Guide: How to Choose the Best Air Purifier

July 12, 2023

Important things to look for when buying an air purifier

Do you really need an air purifier? The answer is a resounding yes. Indoor air can contain microscopic particles (pollutants from outdoor pollution like haze and indoor sources like pet dander, cleaning supplies, cooking particles etc) that are invisible to the human eye and can be hazardous to health.

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As modern homes become better sealed to comply with energy efficiency requirements, pollutants can be trapped inside, and the circulation of airflow is compromised. So, if you want cleaner, fresher air in your home, a good air purifier could be just what you need!

With a plethora of models and variants available on the market, you'll most likely be spoiled for choice. If you're having trouble choosing a suitable air purifier for your home, here are several key factors to consider to ensure you choose the right one for your needs!

Coverage and Efficiency

The most common measure of efficiency is the Clean Air Delivery Rate (CADR). It generally calculates how quickly (per minute) the air can be filtered and cleansed, relative to its cubic area. The higher the number, the faster it cleans. For example, the Sterra Moon air purifier delivers 280 m3/hr of fresh, clean air to your rooms. So if you use it in a 160 sqft room, Sterra Moon can clean the air in it thoroughly in less than 8 minutes.

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You will usually find three CADR numbers, one each assigned to measure the effectiveness of cleaning smoke, dust, and pollen. For haze particles, the ‘smoke’ CADR is the most relevant measure. To ensure that you're purchasing the right air purifier for your space, multiply the width and length of your room by two-thirds, then seek a CADR rating that is roughly two-thirds of that figure.


When shopping for an air purifier, consider buying a unit that has High-Efficiency Particulate Air (HEPA) and activated carbon air filter. Air purifiers with a HEPA filter are considered the gold standard for indoor air purifiers, as they are effective at removing up to 99.97% of harmful airborne particles as small as 0.3 microns. This includes bacteria, mould spores, pet dander, dust, and more. Meanwhile, an activated carbon filter can help eliminate unpleasant odours, so your indoor air remains fresh.

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If you want your air purifier to deal with germs, viruses, mould, and bacteria as well, do consider a unit that also has germicidal ultraviolet lamp technology as it removes these contaminants without any sort of filtration system. Instead, they use ultraviolet light rays to incinerate the bacteria as they pass through.

Caution: Be careful when buying air purifiers with ozone generators and ionisers, as these can produce a small amount of ozone as well as oxidants that can be harmful to your health.

Noise Level

Most air purifiers have internal fans that pull air through a series of filters. Some of these fans are practically silent, especially on low settings. Others make a humming sound as you turn them up.

When shopping for an air purifier, opt for a model with low noise levels, especially if you are going to use it in a bedroom or baby’s room. You'll find noise-level ranges measured in decibels in your device's specs. For a good night’s sleep, look for an air purifier that runs below 30 decibels. The lower, the better!

The Sterra Moon, for example, stands out as one of the quietest air purifiers available on the market, operating at a mere 20 decibels when set to its lowest fan setting.

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Energy Consumption

Since air purifiers run regularly, if not all the time (especially during haze season), you’ll definitely want to choose a model that keeps energy use to a minimum. Most air purifiers have a maximum wattage between 40W and 200W and ideally, the lower the wattage, the better.

The Sterra Moon, for example, is one of the most energy efficient air purifiers on the market, consuming only 45W, which is similar to the energy usage of a light bulb. This contributes to low running costs, saving you thousands of ringgit in the long run.

In addition to wattage, it's worth considering an air purifier that has an Energy Star certification, as this signifies that the air purifier has low electricity consumption.

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Additional Features

Some air purifiers offer additional features like a filter replacement indicator, remote control, automatic mode adjustments based on detected pollutants, timer settings, and smart connectivity. These extras can add convenience to your life, so assess which features are important to you and align them with your needs.

The Sterra Moon air purifier, for example, includes a feature that allows you to monitor the quality of your home's air in real time. Using its LED ring colour indicator, the machine can measure your air quality and display how clean or dirty your air is.

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The average cost of an air purifier ranges from as low as below RM100 to close to RM10,000; depending on brand, additional features, and technology as well as its efficiency and effectiveness in relation to the square footage of your room.

Let’s review three air purifiers of the same brand, Sterra, on the lower, mid, and higher ends of the cost spectrum for a glimpse of what the price tags have to offer:

  1. The most affordable option, the Sterra Mars, retails for RM1,014.00, but you can now get it for RM507.00. It can cover an area up to 107 sqft and it is equipped with three layers of protection. The first layer, pre-filter fabric, filters out hair, dust, lint, and animal fur. The second layer, the True HEPA-13 filter, can trap 99.95% of bacteria, viruses, and allergens while filtering 99.97% of all airborne particles, such as pollen. The third layer, the Activated Carbon filter, aids in the neutralisation of foul odours such as cooking fumes and pet urine odours. It can also absorb formaldehyde, a deadly chemical commonly found in gas stoves, wood furniture, walls, and floors. With a weight of just 2.4kg and dimensions of 21.3 x 21.3cm, this model stands out as the most compact and lightweight option among its counterparts.
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  1. The mid-range option, Sterra Moon, costs RM1,498.00, but you can now get it for RM749.00. It can cover an area of up to 377 sqft. Similarly, the Sterra Moon is equipped with a pre-filter, a True HEPA-13 filtration system, and Activated Carbon filter, but you can purchase the model with Ionizer or UV technology for an extra layer of protection. What makes the Sterra Moon unique is that the model boasts a button-less design. Instead, users can easily turn the device on or off by simply tapping the sensor located on the ControlSphere.
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  1. Last but not least, the Sterra Breeze retails for RM1700.00, but you can now get it for RM1,099.00. It can cover up to 860 sqft and it is also equipped with the pre-filter, a True HEPA-13 filter that hospitals use to decontaminate their rooms and prevent airborne infection, and an Activated Carbon filter to get rid of the smell and odour you don't want in your home. What sets the Strerra Breeze apart from the rest is its night mode, which lets you experience a relaxing, calming light at night when you turn it on. Other features include a Filter Replacement Reminder, which alerts you when it's time to replace your filter.
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In general, all Sterra models feature the same Medical Grade HEPA-13 Filter and offer the same air purifying feature; but the price difference is mainly due to their design, coverage and clean delivery rate.

The Sterra Mars is ideal for compact spaces such as small bedrooms, walk-in wardrobes, bathrooms, or small offices. On the other hand, the Sterra Moon is better suited for average or medium sized bedrooms, while the Sterra Breeze is well-suited for use in larger areas like living rooms, kitchens, or study rooms.

In terms of clean air delivery rate CADR, Sterra Breeze is the most efficient filtering clean air at 400m3/hr, while Sterra Moon filters clean air at 280m3/hr, and Sterra Mars filters clean air at 80m3/hr.


In addition to the purchase price, note the maintenance costs as well. Certain parts, like the filter, will need to be replaced, and the frequency depends on their lifespan. So when buying an air purifier, be sure to take the cost and frequency of future filter replacements into consideration. The filter's lifespan is usually listed in the product specifications. The average cost of filter replacement ranges from as low as RM12.00 to RM755.00 depending on the brand, efficiency, and area coverage.

For instance, all Sterra air purifiers have a lifespan of 2,200 hours before requiring a replacement filter. If the air purifier is used for 6 to 8 hours daily, the filter is estimated to last for 9 to 12 months. Replacing the filter, regardless of model, costs only RM300.00, which is reasonable when compared to similar models on the market. This results in significant long-term savings!

To summarise...

Before shopping for an air purifier, you need to figure out where you want to use the air purifier most frequently so you can get the one that is most suitable for the room size. You should also look at the CADR ratings and filter types (HEPA filters are considered the gold standard for indoor air purifiers!) to get an idea of how effective the air purifier will be for your specific needs.

Once you've identified an air purifier that offers the best filtration for common pollutants in your home and is the right size for your space, evaluate secondary features like noise levels, aesthetics, and additional features. Also, make sure that the air purifier's energy costs and ongoing maintenance costs are within your budget.

To purchase and find out more information about Sterra air purifiers, go to

*The prices listed are correct at the time of writing.

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