The laboratory test is performed by Intertek Testing & Certification and SGS-IBR Laboratories in the UK. The assessment of user friendliness and measurements of noise levels are performed by Intertek and the air cleaning capacity is measured by SGS-IBR. The test protocol is based on official requirements and guidelines and was drawn up in consultation with the laboratories involved.
The laboratory test comprised the following elements:
A. Measurements at 37 dB, or the nearest level below 37 dB:
B. Measurements at max power:
C. User friendliness
The air purifier’s capacity to purify air is tested according to test standard ANSI/AHAM AC-1-2015. The test measures the air purifier’s capacity to eliminate various types of particles (dust and pollen) from the air in a room. The cleaning capacity is stated as the Clean Air Delivery Rate (CADR), which shows the air purifier’s capacity expressed in cubic metres of clean air per hour.
How many square metres the air purifier is able to clean depends on the cleaning capacity (CADR), tied to how many times an hour the room’s volume of air should be purified. According to Asthma Allergy Nordic, an air purifier in a bedroom should clean the air twice an hour. A bedroom of 25 square metres with a ceiling height of 2.4 metres has a volume of 60 cubic metres. In order to purify the air, the air cleaning capacity (CADR) should in this case be at least 120 cubic metres per hour. If you want the air in the room to be cleaned three, four or five times an hour (as some manufacturers and retailers recommend), the air purifier needs a corresponding increase in capacity.
The sound level is an important factor, since the air purifier is often used to clean the air in a bedroom. According to Asthma Allergy Nordic’s guidelines, the air purifier’s cleaning capacity should be considered in relation to the noise it makes. The association recommends that the sound level in a bedroom should not exceed 30 dB(A), which is in line with WHO’s limit for sleep-disturbing background noise.
In the test, the performance of each air purifier is measured at 37 dB(A) and on full power. Before the measurements is taken, the sound level is measured on all power settings to find the power level that produces 37 dB or the nearest level just below that.
The sound level is measured in a controlled laboratory environment. The measurements is carried out 1 metre from the air purifier and from all angles (the air purifier’s sound level is stated as an average value). 37 dB(A) equates to 30 dB(A) from a little over 2 metres, which can be considered a reasonable distance in a normal-sized bedroom of approx. 10 m2.
Most of the air purifiers require relatively little power (W), but since they are intended to run more or less continuously, their energy consumption remains important. The energy consumption is measured at the setting that produced 37 dB(A) and on maximum power.
The assessment of user friendliness includes filter replacement, settings and controls, and displays and menus. The assessment is carried out by experts at the laboratory.
Some air purifiers clean the air using ordinary filters and ionising. Ionising involves the particles in the air being given a negative charge and then sticking to a positively charged metal plate inside the air purifier. If an ionising air purifier charges not only the particles but also the air itself, this forms ozone. Ozone is a health hazard over a certain threshold. The current threshold value for ozone (EU guidelines) is 0.055 ppm (parts per million). The laboratory measures the difference in ozone levels between the input and exhaust air from the various air purifiers.
The measurement results from the test are interpreted in consultation with the laboratory. The grading is based on the laboratory’s test results and uses a 10-point scale, where 10 is the best. A grade of less than 6 is only given if the performance is poor or worse than one might reasonably expect for this type of product.
The grades from the different elements of the test are combined to give an overall grade, using the following weighting:
Measurements at 37 dB, or the nearest level below 37 dB: 45%
Measurements at max power: 45%
User friendliness: 10%