Decide what you are trying to remove and how big the room is first. Then compare products on tested clean air delivery (CADR) at a noise level you will accept, the real filter class and seal quality, carbon mass if odors matter, power use, and the yearly cost of filters. Avoid products that rely on ozone-producing features or that give room sizes without a CADR and test method.
The 12 questions
1. What exactly am I trying to remove?
Particles (smoke, cooking fumes, dust, pollen, pet allergen), gases and odors, or stuffiness? Particles need a particle filter; odors need a sorbent such as activated carbon; stuffiness and high CO₂ need ventilation, not a purifier. See PM2.5, VOCs and CO₂ explained.
Red flag: a product that promises to fix all three with one filter.
2. What is my room volume, and how many clean air changes do I want?
Measure length, width and ceiling height. Multiply by a target of about 5 air changes per hour — more for bedrooms of allergy-sensitive people. The result is the CADR you need in m³/h. Our calculator does this for you.
3. What is the tested CADR — and by which method?
A good answer names the particle type (smoke, dust, pollen), the value in m³/h or CFM, and the test standard, such as AHAM AC-1 or GB/T 18801. Independently certified values (for example through AHAM Verifide) are the most comparable. See CADR explained.
Red flag: "suitable for rooms up to 100 m²" with no CADR, or only an airflow figure.
4. What CADR does it deliver at the speed I will actually use?
Headline CADR is usually measured at maximum speed. Ask for CADR or airflow at each speed, or at least at the speed you expect to use at night or during meetings.
5. Is the filter a classified HEPA — and to which standard?
A good answer is "H13 to EN 1822" or "ISO 35 H to ISO 29463", ideally with a test certificate. "HEPA-type" or "HEPA-like" are not classes. A lower class is acceptable if the CADR is right — but you should know what you are buying. See HEPA H13 explained.
6. Is the filter sealed in the housing?
Look for a continuous gasket and a filter that clamps firmly into place. Leakage around the filter can matter more than the difference between filter classes. A whole-device CADR test captures this; a media-only rating does not.
7. How much carbon is inside, and what type?
If odors or VOCs matter, ask for the carbon weight in grams and whether it is granular or a carbon-impregnated sheet. A few grams of carbon in a fabric layer saturate quickly; hundreds of grams in a granular bed last much longer. See activated carbon explained.
8. How loud is it at the setting I need?
Ask for sound pressure in dB(A) at a stated distance (often 1 m) for each speed. Be cautious with a single "from 20 dB" figure — it usually refers to the lowest speed, which may deliver very little clean air. See noise explained.
9. How much power does it use?
Ask for watts at each speed and in standby. EC (electronically commutated) motors typically use less power for the same airflow than simple AC motors and allow smoother speed control. CADR per watt is a useful efficiency comparison.
10. What do replacement filters cost, and how often?
Get the price of each filter and the manufacturer's replacement interval for your usage. Then calculate the yearly cost (see the worked example below). Check that filters are readily available and likely to remain so.
11. Does it emit ozone or use "active" technologies?
Ionizers, plasma, PCO and some UV lamps can produce ozone or by-products. Prefer mechanical filtration, or at least a device whose active features can be switched off and whose ozone emissions are certified (for example CARB-listed). See ionizers, UV and ozone.
Red flag: "activated oxygen", "super oxygen" or similar wording — these describe ozone.
12. How is it installed, serviced and supported?
For floor units: footprint and clearances. For wall and ceiling units: fixing requirements, power supply and filter access height. For all: warranty length, availability of spare parts, and who to contact for service.
Worked example: annual running cost
Electricity: 30 W × 12 h × 365 days = 131 kWh → 131 × €0.25 ≈ €33 per year
Filters: 2 × €60 = €120 per year
Total: about €153 per year, or roughly €765 over five years — often more than the purchase price.
Run the same calculation for each shortlisted model. A slightly more expensive unit with larger, longer-lasting filters or a more efficient motor can be cheaper over its life.
A simple comparison sheet
| Criterion | Model A | Model B | Model C |
|---|---|---|---|
| CADR (smoke), m³/h, and test method | |||
| Clean ACH in my room at usable speed | |||
| Noise at that speed, dB(A) @ 1 m | |||
| Filter class and standard | |||
| Carbon mass (g) and type | |||
| Power at usable speed (W) | |||
| Annual filter + energy cost | |||
| Ozone-free / certified | |||
| Installation / footprint |
Copy this into a spreadsheet and fill it from product documentation. Where a value is missing, ask the manufacturer; the quality of the answer tells you a lot.
How CEAROX answers these questions
For the CEAROX CX-PRO-580, the product documentation covers the filter configuration (HEPA H13 plus a carbon module), the EC motor, the ceiling installation requirements and the lighting specification. For project-specific questions — room sizing, installation or filter logistics — contact us at office@cearox.com and ask for the current technical documentation.
Key takeaways
- Define the pollutant and the room first; everything else follows.
- Compare tested CADR at a usable noise level, not maximum-speed marketing numbers.
- Check filter class, sealing, carbon mass, power and ozone emissions.
- Calculate annual running cost — filters often cost more than electricity.
Frequently asked questions
What is the most important air purifier specification?
The clean air delivery rate at a noise level you will accept, relative to your room volume. A high-grade filter in a unit that is too small for the room, or too loud to run, will not deliver clean air in practice.
How much does an air purifier cost to run per year?
Add filter replacements to electricity. A unit with filters costing €60 replaced twice a year and drawing 30 W for 12 hours a day at €0.25/kWh costs roughly €150 a year. Check both numbers before buying, because running costs over five years often exceed the purchase price.
Should I avoid purifiers with ionizers?
Not necessarily, but prefer units where the ionizer or other 'active' mode can be switched off and where ozone emissions are certified, for example by CARB in California. Mechanical filtration should do the main work.
Sources and further reading
- ANSI/AHAM AC-1 — Method for measuring performance of portable household electric room air cleaners
- AHAM Verifide — room air cleaner certification programme
- California Air Resources Board — List of CARB-certified air cleaning devices
- EN 1822-1 — High efficiency air filters (EPA, HEPA and ULPA): classification, performance testing, marking
- U.S. EPA — Guide to Air Cleaners in the Home