# Effective Working Area

The effective working area is the room size that the purifier can effectively clean and it is intrinsically related to the Airflow, filter efficiency and room size.

This is the single most important parameter you must look for when looking for an air purifier, as you should buy one that will work well for your room size.

To calculate the effective working area, you need to know the airflow and filter efficiency of the air purifier. If you don’t see these parameters on the specifications table of the product you are intending to buy, the manufacturer or vendor could have just created the effective working area from a random assumption instead of real data.

### How we calculated the Effective Working Area of the AirCleaner Personal

From our tests, and ESRC Validation Report, we know the following parameters:

Filter Efficiency = 99.86%
Airflow = 285m3/h or 167.64 cfm

We can now calculate the Clean Air Delivery Rate (CADR) of the AirCleaner Personal:

Now, according to the Association of Home Appliance Manufacturers, for a room with an 8ft (2.44m) ceiling, the CADR is multiplied by 1.55 to find out the effective working area:

EWA = 167.4*1.55 = 259.47 sqft = 24.1m2

Working backwards, if you know your room size, you can convert that value to sqft and then divide it by 1.55 to get the necessary CADR.

Room volume = 25m2 = 269sqft

You might have seen that manufacturers give the Effective Working Area in a range, for example, 25m2 to 30m2. That’s because rooms are not normally empty, there are beds, wardrobes and stuff around which effectively reduces the total volume of the room.

Knowing the CADR, can also tell us how long the air purifier will take to clean the room. For example, if we have a 25m2 room with a 2.5m ceiling:

Room volume = 25m2*2.5 = 62.5m3 = 2207.16 cft
Minutes to clean the room = room volume/CADR = 2207.16/167.4 = 13min

It is worth saying that these are purely theoretical calculations and in real conditions, there are factors such as leakage, non-ideal air purifier placement and filter ageing which will affect the final CADR of the air purifier.

### This Post Has 2 Comments

1. If the specifications table of an air purifier does not provide information on airflow and filter efficiency, what potential issues could arise in terms of calculating the effective working area? Regards Telkom University

1. Without knowing the airflow it is not possible to calculate the effective working area, as we need to know this value to know how much volume of air is filtered per hour. It can be calculated manually by measuring wind speed with an anemometer and calculating the area of the duct.