In This Guide
The air purifier market is crowded with options and even more crowded with marketing claims. "99.97% of particles!" "Medical-grade filtration!" "Cleans 500 square feet!" What does any of this actually mean for your apartment?
This guide cuts through the noise to help you understand what matters when choosing an air purifier, and what's mostly marketing.
Do You Need an Air Purifier?
Before spending money, consider whether an air purifier will actually help your situation:
Air Purifiers Can Help With:
- Reducing airborne particles (dust, pollen, pet dander)
- Capturing some mold spores
- Reducing cooking smoke and related particles
- Filtering wildfire smoke particles
- Some odors (with activated carbon)
Air Purifiers Can't Fix:
- Humidity problems (you need a humidifier/dehumidifier)
- Odors from continuous sources (cooking, pets—source control is better)
- Poor ventilation (they recirculate, don't add fresh air)
- Settled dust (that requires cleaning)
- Gases like carbon monoxide (that requires detectors and ventilation)
If your main issue is something an air purifier can't fix, save your money and address the actual problem.
What Actually Matters
1. HEPA Filter
True HEPA filters capture 99.97% of particles 0.3 microns and larger. This is the standard you want for particle removal. Avoid "HEPA-like," "HEPA-style," or "HEPA-type" filters—these aren't the same.
See our HEPA Filters Explained guide.
2. CADR Rating
Clean Air Delivery Rate measures how much filtered air the purifier delivers. Higher CADR = more effective for larger spaces or faster cleaning. Look for CADR ratings for smoke, dust, and pollen—smoke CADR is often the most useful single number.
See our CADR Ratings Explained guide.
3. Appropriate Room Size
Match the purifier to your room. "Room size" claims vary wildly—use CADR to calculate: for good cleaning, CADR should be at least 2/3 of your room's square footage. A 300 sq ft bedroom needs CADR of at least 200.
See our Room Size Guide.
4. Noise Level
Especially important for bedrooms. Check noise specs at different speeds. A purifier is useless if it's too loud to run at the speed that actually cleans the air.
See our Quiet Air Purifiers Guide.
5. Operating Costs
Factor in filter replacements (typically every 6-12 months) and electricity. Cheap purifiers with expensive filters aren't actually cheap.
See our Running Costs Guide.
Understanding Filter Types
HEPA (High-Efficiency Particulate Air)
The workhorse for particle removal. Captures particles through a dense mat of fibers. Needs periodic replacement. This is what you want for allergens, dust, and smoke particles.
Activated Carbon
Adsorbs gases and odors onto porous carbon surface. Amount matters—thin carbon sheets do little. Helps with VOCs and smells but doesn't remove particles.
Ionizers
Charge particles so they stick to surfaces. Can produce ozone (a lung irritant). Generally less effective than HEPA and not recommended as primary filtration.
UV-C / Photocatalytic
Marketed to "kill" germs. In consumer air purifiers, air moves too fast for meaningful exposure. Mostly marketing—a good HEPA filter is more practical.
Plasma / Hydroxyl / Other Technologies
Various marketing terms for technologies that often produce some ozone and have limited independent testing. Stick with HEPA unless you have specific reason not to.
Sizing for Your Room
Here's a simple approach:
- Measure your room's square footage
- Look for a purifier with smoke CADR at least 2/3 of that number
- For bedrooms, prioritize low noise at medium speed
- For main living areas, higher CADR is better
| Room Size | Min CADR Needed | Recommended CADR |
|---|---|---|
| 150 sq ft (bedroom) | 100 | 150+ |
| 200 sq ft (small room) | 135 | 200+ |
| 300 sq ft (medium room) | 200 | 300+ |
| 400 sq ft (living room) | 270 | 400+ |
| 500 sq ft (large room) | 335 | 500+ |
Apartment-Specific Considerations
Noise Sensitivity
Apartments mean neighbors and shared walls. A loud purifier at night can be problematic. Check decibel ratings and read reviews about actual noise levels.
Space Constraints
Smaller apartments mean less room for bulky appliances. Tower-style purifiers have smaller footprints. But ensure they have adequate CADR—don't sacrifice performance for size.
No Window Access
Some rooms may lack windows entirely. Air purifiers become more valuable here since you can't just open a window for fresh air.
Shared HVAC
If your apartment shares air with others, you have less control over what enters. A purifier helps with particles that come through shared systems.
Pet Restrictions
Even "no pet" buildings may have allergens from previous tenants or neighbors. If you're sensitive to pet allergens, a HEPA purifier helps.
The One-Room Strategy
You don't need to purify your entire apartment. Many people get the most benefit from a single quality purifier in the bedroom, where they spend 7-8 hours sleeping with the door closed. Start there and add more only if needed.
Frequently Asked Questions
For best results, yes. Air purifiers work by continuously filtering air. Running only occasionally allows particles to accumulate. Modern purifiers are designed for continuous use and use modest electricity.
It depends what you're paying for. Higher CADR and better build quality can justify higher prices. Smart features and aesthetics are personal preference. But HEPA filtration works the same regardless of price—physics is physics. Don't pay premium prices for marketing terms.
Technically possible for small apartments with open floor plans. But closed doors block airflow, and distant rooms get limited benefit. Most people do better with a properly-sized purifier in the most important room (usually bedroom) rather than an oversized unit trying to clean everything.