Feb
Many air purifiers advertise the “room coverage” or “room size” for their room air purifiers, but could they be relied on when deciding on which air purifier to buy? Let’s find out.
What does room coverage mean?
Room coverage is usually listed in m², or square meters. It supposedly tells you the maximum size of a room that an air purifier can support.
The problems with room coverage
The main problem with room coverage is that every manufacturer has their own way of calculating room coverage.
Generally speaking, here is how room coverage is calculated by manufacturers:
Room Coverage (m²) = Clean Air Delivery Rate [CADR] at maximum speed (m³/h) ÷ Air Changes per Hour (ACH) ÷ Room Height (m)
Clean Air Delivery Rate, or CADR, tells us the volume of air cleaned per hour after factoring in filtration efficiency, air flow, and air pressure of the device.
Air Changes per Hour, or ACH, is the equivalent number of times the air in a room is ventilated or cleaned.
According to the formula, the maximum Clean Air Delivery Rate (CADR) of the air purifier at the highest and loudest speed is divided by the number of Air Changes per Hour, and is finally divided by the floor-to-ceiling height of the room to get the room coverage.
The main problem is the number used for Air Changes per Hour (ACH) may vary widely between different companies – Company A may calculate their room coverage based on 3 ACH, Company B may use 5 ACH, Company C may use 1 ACH, and so on.
To better illustrate this problem, imagine a scenario where Companies A, B, and C are selling an air purifier that has the same performance (300 m³/h CADR). CADR tells us the overall air-cleaning performance of an air purifier.
Company A, basing their calculations on 3 ACH, recommends using their air purifier in a 38 m² room.
Company B, basing their calculations on 5 ACH, recommends 23 m².
Company C, using 1 ACH, recommends 115 m².
Even though all three air purifiers have the same performance, Company C will appear to have the best product because they calculated their room coverage based on 1 ACH, giving customers the false impression that their product is better than the other two companies.
That is the main reason why room coverage shouldn’t be relied on.
Use CADR and ACH instead of room coverage
Instead of using room coverage, you should use CADR to compare the performance of various room air purifiers, and ACH to determine whether the air purifier is delivering sufficient clean air in your room.
Keep in mind that most air purifier companies only list the CADR at the highest setting, which is also the nosiest setting. You will need to find out what the CADRs are for the other speeds if such information isn’t readily available.
We recommend homes and businesses to have at least 6 ACH in all of their indoor spaces. This is in line with the Singapore NEA’s recommendation of having at least 5 – 7 ACH.
For example, if you are buying a single air purifier for a 20 m² room, it should be running at a speed with a minimum CADR of 312 m³/h.
You can easily calculate the Air Changes per Hour in a room with our calculator here.
Conclusion
The room coverage metric shouldn’t be used when choosing a room air purifier, as different companies use different yardsticks to measure room coverage, and some companies may even ‘inflate’ their numbers by purposely using a very low ACH during their calculation process.
Instead of using room coverage, use CADR to compare the performance of different air purifiers, and use ACH to check whether it will deliver sufficient clean air in your room.
Now that you understand the problems with room coverage, it’s time to check out the best air purifiers for your home or business in Singapore.
Room Air Purifier
