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When choosing an air purifier, understanding its cleaning capacity is just as important as understanding its filtration technology.
Air purifiers come with several specifications, from HEPA filtration to smart sensors and multiple fan speeds.
Among these, one specification deserves particular attention: CADR, or Clean Air Delivery Rate.
But what exactly does CADR mean, and why should you consider it before buying an air purifier?
CADR stands for Clean Air Delivery Rate.
It measures how much cleaned air an air purifier delivers over a specific period under standardised testing conditions.
CADR is commonly expressed in cubic metres per hour (mĀ³/h).
For example, an air purifier with a CADR of 400 mĀ³/h delivers a greater volume of particle-cleaned air per hour than a purifier rated at 200 mĀ³/h, assuming comparable test conditions.
Simply put, higher CADR generally means faster airborne particle removal.
Indoor air can contain airborne particles from several sources, including:
Fine dust and particulate matter
Pollen entering from outdoors
Airborne pet dander
Particles released during cooking
Dust stirred up by everyday household activities
An air purifier continuously processes indoor air to help reduce these particles.
Its CADR provides an indication of how quickly it can do so.
A purifier with insufficient cleaning capacity may take longer to reduce particle concentrations, particularly in larger rooms.
CADR becomes especially useful when considered alongside room volume.
For example, imagine a room measuring 5 metres long, 4 metres wide and 3 metres high.
Its volume is:
5 Ć 4 Ć 3 = 60 mĀ³
If an air purifier has a CADR of 300 mĀ³/h, its theoretical equivalent air change rate is:
300 Ć· 60 = 5 air changes per hour
This provides a useful starting point for assessing whether the purifier is appropriately sized.
Actual cleaning performance will vary depending on airflow, room layout, pollutant sources and fan settings.
Not necessarily.
While CADR is an important performance indicator, it should not be the only factor influencing your decision.
Consider these additional features:
Filtration technology: An effective particle filter, such as an appropriate HEPA filter, helps capture fine airborne particles.
Noise levels: A high-capacity purifier should also be comfortable to operate in everyday environments.
Energy consumption: Power efficiency matters when an air purifier operates for extended periods.
Smart features: Air quality sensors and automatic fan adjustment can improve convenience.
Maintenance: Accessible replacement filters and clear maintenance requirements support long-term performance.
The best air purifier balances cleaning capacity with the needs of the room and its occupants.
CADR and HEPA describe two different aspects of air purification.
HEPA filtration refers to the efficiency of a filter at capturing particles under specified test conditions.
CADR describes the rate at which the complete air purifier delivers cleaned air.
A high-efficiency filter alone does not guarantee high CADR. The purifier's airflow design and fan performance also affect the amount of air it can process.
Both specifications are worth considering when comparing air purifiers.
Whether you're looking for an air purifier for a bedroom, living room or larger indoor space, CADR can help you compare different models more meaningfully.
Glen Air Purifiers offer different cleaning capacities across the range, allowing you to choose according to your room requirements.
Before purchasing, review the model's CADR, recommended room coverage and filtration specifications.
Because cleaner indoor air isn't just about filtration. It's also about how effectively your purifier delivers it.
Explore Glen Air Purifiers and choose the cleaning capacity that suits your home.
Made better in Glen.
05 Nov 2026
A bigger air purifier isn't always the right choice. The right one is designed to clean the air effectively in the space where you use it.
When buying an air purifier, most people focus on features such as HEPA filters, smart sensors and design. But one of the most important factors is often overlooked: room size.
An air purifier that works well in a small bedroom may not deliver the same results in a spacious living room. Understanding your room dimensions and the purifier's cleaning capacity can help you make a more informed decision.
Air purifiers continuously draw in surrounding air, pass it through their filtration system and release filtered air back into the room.
The larger the room, the more air the purifier needs to process to achieve a given number of air changes per hour.
If an air purifier is undersized, it may struggle to clean the air quickly enough, particularly when pollution levels are high.
Choosing a properly sized purifier helps ensure more effective performance without unnecessarily operating the appliance at its highest fan speed.
Start by calculating the floor area of the room.
Room Area = Length Ć Width
For example, a bedroom measuring 12 feet by 15 feet has an area of 180 square feet.
However, floor area alone doesn't tell the whole story. Ceiling height also matters because it determines the total volume of air in the room.
A room with a high ceiling contains more air than a room with the same floor area and a standard ceiling.
Air Changes Per Hour, or ACH, indicates how many times an air purifier can theoretically process an amount of air equivalent to the room's volume in one hour.
For example, an ACH of 4 means the purifier processes an air volume equivalent to the room's total volume approximately four times per hour.
For effective particle reduction, choosing a purifier capable of around 4ā5 equivalent air changes per hour is a useful starting point, depending on the application.
The actual results will depend on room layout, airflow, pollutant sources and operating speed.
Clean Air Delivery Rate (CADR) indicates the volume of filtered air an air purifier can deliver per unit of time.
It is usually expressed in cubic metres per hour (mĀ³/h).
A higher CADR generally means the purifier can remove airborne particles more quickly under comparable test conditions.
For example, a purifier rated at 300 mĀ³/h can theoretically provide five equivalent air changes per hour in a 60 mĀ³ room.
This makes CADR one of the most useful specifications when matching an air purifier to a room.
Different rooms have different air quality requirements.
Bedrooms: Consider quiet operation, sleep mode and appropriate cleaning capacity for overnight use.
Living rooms: Larger spaces may benefit from higher CADR, particularly when several people regularly occupy the room.
Home offices: Compact dimensions, quiet operation and efficient particle filtration can make an air purifier suitable for daily use.
Open-plan spaces: Connected rooms may require greater cleaning capacity or multiple air purifiers to provide effective coverage.
Even a properly sized air purifier needs suitable placement.
Position it where air can circulate freely, without blocking the intake or outlet.
Avoid placing the purifier directly against curtains, behind furniture or in tightly enclosed corners.
Always follow the manufacturer's recommended clearance and positioning instructions.
Glen offers air purifiers with different cleaning capacities and features to suit different indoor environments.
When selecting a model, compare its recommended coverage, CADR, filtration technology and noise levels.
The right air purifier isn't simply about choosing the biggest model. It's about choosing the right cleaning performance for your room.
Explore the Glen Air Purifier range to find a model suited to your space.
Made better in Glen.
05 Nov 2026
When we think about air pollution, we often picture busy roads, vehicle emissions and smog-filled skies. But what about the air inside our homes?
While closing doors and windows may help keep some outdoor pollutants away, indoor air isn't necessarily free from pollution. Everyday activities such as cooking, cleaning and spending time with pets can introduce airborne particles into our living spaces.
Understanding where these pollutants come from is the first step towards creating a cleaner indoor environment.
1. Cooking: More Than Just Smoke and Odours
Cooking brings families together, but it can also introduce pollutants into indoor air.
Frying, grilling and high-temperature cooking can release smoke, fine particulate matter and other airborne pollutants. Even when visible smoke disappears, some particles may remain suspended in the air.
What can help?
2. Pets: The Invisible Allergens Around Us
Pets bring companionship and happiness into our homes. However, they can also contribute to indoor airborne allergens.
Pet dander consists of tiny particles of shed skin that may become airborne or settle on furniture, carpets and bedding. Pets can also carry pollen and dust indoors on their fur.
For people sensitive to these allergens, maintaining cleaner indoor air can be particularly important.
What can help?
3. Daily Activities: Dust You May Not Even Notice
Walking across carpets, making beds, dusting furniture and cleaning the house can all stir settled particles back into the air.
Household dust can contain a mixture of fibres, skin flakes, pollen and other fine particles. Some may remain airborne long enough to be inhaled.
What can help?
4. Outdoor Air: Pollution Can Find Its Way Inside
Closing your windows doesn't necessarily mean outdoor pollution stays outside.
Fine particulate matter, including PM2.5, can enter homes through open doors, windows, ventilation systems and gaps around building structures.
During periods of poor outdoor air quality, these particles may contribute significantly to indoor pollution levels.
What can help?
How Can an Air Purifier Help?
While regular cleaning and ventilation are important, an air purifier can provide an additional layer of protection against airborne particles.
Glen Air Purifiers with H13 HEPA filtration are designed to capture fine airborne particles, including dust, pollen and certain allergens, as air passes through the filter.
Depending on the model, additional filtration and smart features can help make everyday indoor air management more convenient.
When choosing an air purifier, consider your room size, Clean Air Delivery Rate (CADR), filtration technology and filter maintenance requirements.
Cleaner Indoor Air Starts With Awareness
Indoor air pollution doesn't always come from obvious sources. Sometimes, it is part of the everyday activities that make a house a home.
Understanding these sources, improving ventilation where appropriate, cleaning regularly and using effective air filtration can all contribute to better indoor air quality.
Don't just check the AQI. Change your Indoor Air.
Explore the Glen Air Purifier range and find a solution suited to your home.
Made better in Glen.
05 Nov 2026
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