Best Air Purifiers Under $300

Most air purifiers under $300 deliver the same CADR performance as units costing twice as much. The filter replacement cost, not the purchase price, determines what you actually spend over three years.

A $200 unit with $60 annual filters costs $380 over three years. A $280 unit with $25 annual filters costs $355 over the same period. The cheaper unit is not cheaper.

This guide covers the five best True HEPA air purifiers available for under $300 right now: budget compact units for bedrooms, mid-range workhorses for living spaces, and high-CADR performers that rival premium models. Every recommendation includes AHAM-certified smoke CADR ratings, verified noise levels at each fan speed, and the real annual filter and electricity cost, not just the sticker price.

The sub-$300 price bracket is the sweet spot for air purifier value. Above $300, you pay for smart features, larger coverage, or brand premium, not meaningfully better filtration per dollar.

Below $150, you sacrifice CADR performance, filter quality, or noise control. The $150 to $300 range delivers True HEPA filtration with AHAM-certified smoke CADR between 145 and 246 CFM, enough for rooms from 150 to 360 square feet at the standard 2 ACH rate.

For allergy and asthma sufferers who need 5 ACH, the same units effectively cover rooms from 60 to 144 square feet. Always calculate your target CADR at 5 ACH if you have respiratory conditions, regardless of the manufacturer’s stated coverage area at 2 ACH.

The difference between a $150 unit and a $280 unit in this bracket is rarely filtration quality. It is CADR capacity, noise level at equivalent fan speeds, and filter replacement cost. A Levoit Core 300S at $99 and a Coway AP-1512HH at $200 both use True HEPA H13 filtration. The Coway delivers 70% more smoke CADR, covers a larger room, and costs roughly the same per year in filters.

Use the bar chart above to compare the true first-year cost of each unit. The Blueair Blue Pure 211+ costs the most upfront and has the highest annual filter cost, but it also delivers the highest smoke CADR in this group at 350 CFM.

What Makes a Great Air Purifier Under $300

A great air purifier under $300 has three non-negotiable features: AHAM-certified smoke CADR appropriate for your room size, True HEPA filtration (H13 or higher), and CARB certification confirming ozone output below 0.050 ppm. Everything else is secondary.

Smoke CADR is the most important spec because smoke particles (0.09 to 1.0 microns) are the hardest to capture. A unit that performs well on smoke CADR will perform well on dust and pollen too. According to AHAM AC-1 testing methodology, smoke CADR measures the clean air delivery rate for the smallest standardized test particles.

The CARB certification matters because some budget air purifiers, particularly older ionizer models, emit ozone as a byproduct. CARB CCR Title 17 sets the legal limit at 0.050 ppm. Any unit sold in California must meet this standard, but not all online retailers enforce it. Always check for CARB certification before buying, especially on marketplace listings.

Noise level is the third critical factor that separates good sub-$300 units from great ones. A unit that delivers 200 CFM at 55 dB is fine for a living room. The same unit in a bedroom at night is unusable. The best sub-$300 units achieve sleep modes between 24 and 30 dB, which is quieter than a whisper at 30 dB.

Top 5 Air Purifiers Under $300: Detailed Reviews

Coway AP-1512HH: Best Overall Air Purifier Under $300

The Coway AP-1512HH delivers 246 CFM smoke CADR at a street price of approximately $200. It carries AHAM Verifide certification, CARB certification, and the Asthma and Allergy Foundation of America (AAFA) certification, making it the most independently verified unit in this price range.

Key Specifications:

• Smoke CADR: 246 CFM (AHAM certified)
• Coverage at 2 ACH: 360 sq ft
• Coverage at 5 ACH: 144 sq ft
• Sleep mode noise: 30 dB
• Annual filter cost: approximately $30

The AP-1512HH uses a four-stage filtration system: washable pre-filter, activated carbon filter, True HEPA H13 filter, and an optional ionizer that can be switched off. The ionizer is off by default, which is the correct setting for anyone with asthma or chemical sensitivity.

At 30 dB in sleep mode, the Coway is audible but not disruptive. The auto mode uses a particle sensor to adjust fan speed based on real-time PM2.5 readings. In independent testing, the sensor responds to cigarette smoke and cooking fumes within 30 seconds, ramping the fan to high speed until particulate levels drop.

The annual filter cost of approximately $30 is among the lowest for any unit with 200+ CFM smoke CADR. Genuine Coway replacement filters are widely available and rarely out of stock, unlike some competitors that use proprietary filter shapes available from a single source.

For most home users, the Coway AP-1512HH is the best sub-$300 air purifier because it combines the highest verified CADR with the lowest filter cost and the most independent certifications of any unit in this price bracket.

Winix 5500-2: Best for Pet Owners and Heavy Odor Control

The Winix 5500-2 delivers 243 CFM smoke CADR at approximately $180. It matches the Coway AP-1512HH on CADR performance while adding a dedicated odor-control layer: a washable activated carbon filter grid that provides more carbon surface area than most competitors in this price range.

Key Specifications:

• Smoke CADR: 243 CFM (AHAM certified)
• Coverage at 2 ACH: 360 sq ft
• Coverage at 5 ACH: 144 sq ft
• Sleep mode noise: 27 dB
• Annual filter cost: approximately $50

The Winix uses a three-stage system plus PlasmaWave technology, which generates hydroxyl ions to neutralize bacteria and viruses. PlasmaWave is CARB certified and produces no measurable ozone, unlike older ionizer technologies. You can disable it with a button if you prefer mechanical filtration only.

The 5500-2 is quieter than the Coway at sleep mode (27 dB vs 30 dB), which matters for light sleepers. The tradeoff is a higher annual filter cost of approximately $50 per year, driven by the more elaborate carbon filter grid. For homes with pets, cooking odors, or smokers, the extra carbon capacity justifies the higher running cost.

The Winix 5500-2 is the best sub-$300 choice for pet owners because its activated carbon filter captures pet odors that True HEPA alone cannot address. The washable pre-filter captures visible pet hair, extending the life of the HEPA filter.

Levoit Core 400S: Best Smart Air Purifier Under $300

The Levoit Core 400S delivers 260 CFM smoke CADR at approximately $220. It is the only unit in this roundup with a full smart home integration suite: Wi-Fi connectivity, the VeSync app for remote control, voice control via Alexa and Google Assistant, and real-time PM2.5 monitoring displayed on the unit and in the app.

Key Specifications:

• Smoke CADR: 260 CFM (manufacturer rated, not AHAM certified)
• Coverage at 2 ACH: 403 sq ft
• Coverage at 5 ACH: 161 sq ft
• Sleep mode noise: 24 dB
• Annual filter cost: approximately $40

The Core 400S uses a cylindrical True HEPA H13 filter with an integrated activated carbon layer. The 360-degree intake design allows placement anywhere in a room without worrying about directional airflow. At 24 dB in sleep mode, it is the quietest unit in this roundup and effectively silent in most bedrooms.

One limitation: the Core 400S smoke CADR is manufacturer-rated, not AHAM Verifide certified. Levoit’s internal testing methodology is not independently verified, which means the stated 260 CFM may not directly compare to AHAM-certified ratings from Coway or Winix. For most users, the difference is negligible. For those who prioritize independent verification, the Coway or Winix are better choices.

The Levoit Core 400S is the best choice if you want app control, scheduled operation, and real-time air quality data without exceeding $300. The VeSync app shows PM2.5 trends over time, which helps you identify pollution sources in your home, such as cooking, candle burning, or outdoor infiltration during high-AQI days.

Levoit Core 300S: Best Budget Air Purifier Under $150

The Levoit Core 300S delivers 145 CFM smoke CADR at approximately $99. It is the best option for small bedrooms, home offices, and nurseries where a full-size unit would be overkill on both cost and noise.

Key Specifications:

• Smoke CADR: 145 CFM (manufacturer rated)
• Coverage at 2 ACH: 219 sq ft
• Coverage at 5 ACH: 87 sq ft
• Sleep mode noise: 24 dB
• Annual filter cost: approximately $25

The Core 300S uses the same cylindrical H13 True HEPA filter design as the Core 400S, scaled down for smaller rooms. At $25 per year for genuine replacement filters, it has the lowest running cost of any unit in this roundup. The annual electricity cost is approximately $9 at 13 cents per kWh running 8 hours daily.

The 145 CFM smoke CADR limits the Core 300S to rooms under 220 square feet at 2 ACH. For allergy sufferers needing 5 ACH, the effective coverage drops to 87 square feet, which is a small bedroom or nursery. Do not buy this unit for a living room or open-plan space. It will run continuously on high speed and still fail to achieve the recommended air changes.

The Core 300S is the best choice for a bedroom under 200 square feet where budget is the primary concern. It delivers genuine True HEPA filtration, smart features via the VeSync app, and the lowest total cost of ownership of any air purifier on the market.

Blueair Blue Pure 211+: Best High-CADR Unit Under $300

The Blueair Blue Pure 211+ delivers 350 CFM smoke CADR at approximately $250. It is the highest-CADR unit available under $300 and the only one in this roundup suitable for large living rooms, open-plan spaces, and whole-floor coverage in smaller homes.

Key Specifications:

• Smoke CADR: 350 CFM (AHAM certified)
• Coverage at 2 ACH: 540 sq ft
• Coverage at 5 ACH: 216 sq ft
• Sleep mode noise: 31 dB (lowest of three speeds)
• Annual filter cost: approximately $60

The Blue Pure 211+ uses HEPASilent technology, which combines electrostatic charging with mechanical filtration. According to AHAM testing, it achieves 350 CFM smoke CADR while consuming only 30 to 60 watts depending on fan speed. The tradeoff is a higher annual filter cost of approximately $60 and a single-speed design with no true sleep mode, just a low setting at 31 dB.

The washable fabric pre-filter comes in multiple colors, which is a design feature some users value. More importantly, the pre-filter captures large particles including pet hair and dust, extending the life of the main filter. The unit is CARB certified and ENERGY STAR certified.

The Blue Pure 211+ is the best choice for large rooms over 350 square feet where a standard 200 CFM unit would be undersized. At 350 CFM smoke CADR, it achieves 2 ACH in a 540-square-foot space, which covers most living rooms and open-plan kitchen-dining combinations.

Use the comparison table above to find the unit that matches your room size and budget. For most buyers, the Coway AP-1512HH or Winix 5500-2 offer the best combination of verified CADR, low noise, and reasonable filter costs.

How to Choose the Right Air Purifier for Your Room Size

Room size, not budget, should determine which air purifier you buy. A unit that is too small for your room will run continuously on maximum speed, generate more noise, and still fail to achieve the recommended air changes per hour. The result is PM2.5 levels that stay elevated even when the purifier is running.

CADR is the specification that connects room size to cleaning speed. The formula is: smoke CADR needed equals room length in feet times room width in feet times ceiling height in feet times target ACH, divided by 60. For a standard 8-foot ceiling, the simplified formula is room area times 8 times ACH divided by 60.

Most manufacturers rate their coverage area at 2 ACH, which is the minimum standard for general indoor air quality improvement. Allergy and asthma sufferers should target 5 ACH, which requires 2.5 times more CADR for the same room. A unit rated for 360 square feet at 2 ACH covers only 144 square feet at 5 ACH.

This distinction is the most common cause of underperforming air purifiers. Buyers purchase a unit based on the manufacturer’s stated coverage area, place it in a room that size, and do not achieve the air quality improvement they expected. The fix is to calculate CADR at your target ACH before buying, not after.

Use the calculator above to find your minimum smoke CADR requirement. Then match it to the closest unit in the comparison table. If your calculated CADR exceeds 350 CFM at your target ACH, you need either a single high-CADR unit above the $300 price point or two sub-$300 units working together in the same space.

Filter Replacement Cost: The Hidden Expense

Filter replacement cost, not the purchase price, determines the total cost of owning an air purifier. A $99 unit with $60 annual filters costs $279 over three years. A $200 unit with $30 annual filters costs $290 over the same period. The total cost difference is negligible, but the $200 unit delivers higher CADR and better filtration.

Genuine replacement filters cost more than third-party alternatives, but they maintain the manufacturer’s stated CADR and filtration efficiency. Third-party filters may fit the housing, but independent testing shows they often reduce CADR by 15 to 30 percent due to lower-quality media or poor sealing around the filter frame. For the full breakdown of filter and electricity costs across brands, see our guide on total annual cost of ownership including filters and power consumption.

Filter replacement intervals vary by usage and pollution level. In a home with pets, the pre-filter may need cleaning every two weeks and the HEPA filter may need replacement every 8 to 10 months instead of the manufacturer’s stated 12 months. During wildfire season with sustained AQI above 150, HEPA filters load faster and should be checked at 50 percent of the normal interval.

The washable pre-filter is the most underrated feature on sub-$300 units. Both the Coway AP-1512HH and Winix 5500-2 include washable pre-filters that capture visible dust, pet hair, and larger particles before they reach the HEPA stage. Cleaning the pre-filter every two to four weeks extends HEPA filter life by 30 to 50 percent, directly reducing your annual filter cost.

Noise Level: What dB Ratings Actually Mean for Daily Use

Noise level in decibels is a logarithmic scale. A 3 dB increase represents a doubling of sound energy. A unit rated at 30 dB is twice as loud as one rated at 27 dB, and a unit at 54 dB on turbo mode is roughly four times as loud as the same unit at 30 dB on sleep mode.

For bedroom use, target 30 dB or below at the fan speed that achieves your target ACH. The Levoit Core 400S and Core 300S both achieve 24 dB at sleep mode, which is effectively silent in a room with any ambient noise. The Coway AP-1512HH at 30 dB is audible but not disruptive for most sleepers. The Blueair Blue Pure 211+ at 31 dB on its lowest setting is the loudest of the group and may be noticeable in a quiet bedroom.

For living room use, noise tolerance is higher. A unit running at 45 to 50 dB on medium speed is comparable to background conversation or a refrigerator compressor. At this level, you can watch television or have a conversation without raising your voice. The tradeoff is CADR: higher fan speeds produce more noise but also more clean air delivery.

Certifications That Matter: CARB, AHAM, and ENERGY STAR

Three certifications separate legitimate air purifiers from marketing claims. CARB certification confirms the unit emits less than 0.050 ppm ozone. AHAM Verifide confirms the CADR rating was tested by an independent laboratory using the ANSI/AHAM AC-1 standard. ENERGY STAR certification confirms the unit meets EPA efficiency standards and will cost approximately $9 to $45 per year to run at 13 cents per kWh.

CARB certification is mandatory for units sold in California, but online retailers do not always enforce it. Before buying any air purifier, check the CARB certified device list at the California Air Resources Board website. If a unit is not listed, it may emit ozone above the legal limit, especially if it uses ionization or electrostatic precipitation as a primary filtration method.

AHAM Verifide is the only independent verification of CADR performance. Manufacturer-stated CADR without AHAM certification may use different testing conditions, different particle sizes, or different calculation methods. The Levoit Core 400S and Core 300S, for example, state CADR based on manufacturer testing, not AHAM verification. Their stated CADR values are likely accurate but not directly comparable to AHAM-certified units from Coway and Winix.

ENERGY STAR certification is less critical for filtration quality but important for running cost. An ENERGY STAR certified unit like the Coway AP-1512HH uses approximately 40 watts on medium speed. A non-certified unit with the same CADR may use 60 to 80 watts, adding $15 to $25 per year to your electricity bill at 13 cents per kWh running 8 hours daily.

Brand Comparisons for Sub-$300 Buyers

If you are deciding between two specific brands in this price range, the comparison usually comes down to CADR versus filter cost. Coway units typically deliver higher verified CADR with lower filter costs. Winix units match Coway on CADR but add more activated carbon for odor control at a higher filter replacement cost. For a detailed head-to-head comparison, see our guide on Coway versus Winix across CADR, noise, and long-term filter expenses.

Levoit offers the best smart features and app integration at the expense of independent CADR verification. The Core 400S and Core 300S are excellent units, but their CADR figures are not AHAM-certified. For a full breakdown of how Levoit compares to Coway on filtration quality, noise, and total cost, read our Levoit versus Coway comparison covering CADR, smart features, and long-term value.

Blueair competes on raw CADR output. The Blue Pure 211+ at 350 CFM smoke CADR outpaces every other sub-$300 unit. The tradeoff is higher filter cost and a less refined noise profile. If you need maximum CADR for a large room and filter cost is secondary, Blueair is the right choice. If you want the best overall value, Coway or Winix are better options. For more on this, see our Blueair versus Coway analysis comparing CADR output against total ownership cost.

Honeywell and Dyson rarely compete in the sub-$300 bracket. Honeywell units in this price range tend to have lower CADR and louder operation than the Coway or Winix equivalents. Dyson units start above $300 and prioritize design and multi-functionality over filtration performance per dollar. Our Honeywell versus Dyson comparison covers why neither brand is the best value in the sub-$300 segment.

Medify competes in the sub-$300 range with the MA-40, which delivers 220 CFM smoke CADR at approximately $250. The Medify uses medical-grade H13 HEPA filtration and targets users who prioritize filtration grade over CADR output. For a direct comparison of filtration quality, coverage, and filter costs, see our Levoit versus Medify breakdown covering HEPA grade, CADR, and warranty differences.

How to Verify Your Air Purifier Is Working

The only way to confirm your air purifier is working is to measure PM2.5 levels before and after running the unit. A PM2.5 air quality monitor costs $50 to $100 and shows you exactly what your purifier is doing in real time. Without a monitor, you are guessing based on subjective air quality perception, which is unreliable.

Run the monitor for 24 hours without the purifier to establish a baseline. Then run the purifier on medium speed for 30 minutes and check the PM2.5 reduction. A properly sized unit should reduce PM2.5 by 70 to 85 percent within 30 minutes at 5 ACH. If the reduction is less than 50 percent, the unit is undersized for the room or the filter needs replacement.

Common causes of poor performance include: placing the unit in a corner (reduces effective coverage by 20 to 30 percent), running the unit on low speed in a room larger than its rated coverage at that speed, and using a filter that is past its replacement interval. The fix for all three is straightforward: move the unit to a central location, match fan speed to room size, and replace filters on schedule.

What Is the Difference Between True HEPA and HEPA-Type Filters?

True HEPA filters capture 99.97 percent of particles at 0.3 microns as defined by IEST standards. HEPA-type filters have no standardized test requirement. Some HEPA-type filters capture 99 percent of particles at 2.5 microns, which means they miss the smallest and most harmful particles including fine wildfire smoke (0.09 to 1.0 microns) and virus-carrying aerosols.

The difference matters most for allergy sufferers and anyone in a wildfire-prone region. Pollen particles range from 10 to 100 microns and are easy to capture. Wildfire smoke particles range from 0.09 to 1.0 microns and require True HEPA or better to capture effectively. A HEPA-type filter that captures 99 percent of pollen may capture only 50 to 70 percent of wildfire smoke particles.

All five units recommended in this guide use True HEPA H13 filters. The Coway, Winix, and Blueair units carry AHAM certification confirming their CADR ratings with the installed filters. The Levoit units use H13-grade media but lack independent AHAM verification of their CADR claims.

Can I Run an Air Purifier 24/7?

Yes, you can and should run an air purifier 24 hours per day. Indoor air quality is not static. Cooking, cleaning, walking on carpet, opening doors, and outdoor air infiltration all introduce new particles continuously. Turning the purifier off for eight hours allows PM2.5 levels to climb back to ambient levels, undoing the filtration work from the previous 16 hours.

The electricity cost of continuous operation is low. A unit consuming 40 watts running 24 hours per day at 13 cents per kWh costs approximately $45 per year. Running the same unit 8 hours per day costs approximately $15 per year. The $30 annual difference is negligible compared to the health benefit of continuous filtration.

Use auto mode if your unit has it. Auto mode adjusts fan speed based on real-time particle sensor readings, running on low or sleep mode when PM2.5 is low and ramping up when pollution spikes. This balances filtration effectiveness with noise and energy use better than manual fan speed selection.

Why Does My Air Purifier Smell Like Plastic or Chemicals?

A new air purifier that smells like plastic or chemicals is off-gassing volatile organic compounds from the manufacturing process. This is common with units that use substantial amounts of new plastic, adhesives, or foam seals. The smell typically dissipates within 48 to 72 hours of continuous operation in a well-ventilated room.

If the smell persists beyond one week, it may indicate the activated carbon filter is saturated from absorbing manufacturing VOCs. Replace the carbon filter if the unit has a separate carbon stage. If the smell is sour or musty rather than chemical, the HEPA filter may have absorbed moisture during storage or shipping. Replace the HEPA filter and inspect the unit interior for mold or mildew before installing the new filter.

A smell like chlorine or a sharp electrical odor after the first week of operation is not normal. It may indicate an ionizer producing ozone above the CARB limit of 0.050 ppm. Disable the ionizer immediately if your unit has one. If the smell persists with the ionizer off, the unit may have an electrical fault and should be returned or replaced.

Do I Need an Air Purifier With an Ionizer?

No, you do not need an ionizer. Ionizers charge particles so they stick to surfaces rather than remaining airborne. This removes particles from the air you breathe but deposits them on walls, furniture, and floors where they can be resuspended by movement or cleaning. A True HEPA filter removes particles from the environment entirely by trapping them in the filter media.

Ionizers also produce ozone as a byproduct of the corona discharge process used to generate ions. CARB limits ozone output to 0.050 ppm, and most modern ionizers stay below this threshold. However, even low-level ozone can irritate the airways of people with asthma or chemical sensitivity. For these users, the safest choice is a unit with the ionizer disabled or a unit that does not include one at all.

The Coway AP-1512HH and Winix 5500-2 both include ionizers that can be switched off. The Levoit Core 400S and Core 300S do not include ionizers. The Blueair Blue Pure 211+ uses electrostatic charging in the filter media itself, which is different from a standalone ionizer and does not produce measurable ozone.

How Often Should I Replace My Air Purifier Filter?

HEPA filters should be replaced every 12 months under normal household conditions. Activated carbon filters should be replaced every 6 months. Washable pre-filters should be cleaned every 2 to 4 weeks. These are manufacturer-recommended intervals, and real-world conditions may require more frequent replacement.

Homes with pets, smokers, or located in wildfire-prone regions should replace HEPA filters every 6 to 8 months. During sustained high-AQI events (AQI above 150), check HEPA filters at 50 percent of the normal interval. A filter that is visibly gray or brown, or one that emits a musty odor when the unit runs, needs immediate replacement regardless of the calendar interval.

Running a saturated filter reduces CADR by 20 to 50 percent and increases energy consumption because the fan motor works harder to pull air through the loaded media. A filter that is visibly dirty is already past its useful life. Replace it promptly to maintain the CADR and filtration efficiency you paid for.

What Size Air Purifier Do I Need for a 12×12 Bedroom?

A 12×12 bedroom with an 8-foot ceiling has a volume of 1,152 cubic feet. At 2 ACH for general use, you need a smoke CADR of approximately 38 CFM. At 5 ACH for allergy or asthma management, you need a smoke CADR of approximately 96 CFM. Any unit in this guide meets the 2 ACH requirement. The Levoit Core 300S at 145 CFM is the smallest unit that meets the 5 ACH requirement for a 12×12 room.

If you have allergies or asthma, choose the Levoit Core 300S or step up to the Coway AP-1512HH for additional headroom. The Coway at 246 CFM smoke CADR achieves 5 ACH in a room up to 144 square feet with an 8-foot ceiling, which covers most bedrooms. Running a unit with excess CADR capacity on a lower fan speed is quieter and more energy-efficient than running an undersized unit on maximum speed.

Is a More Expensive Air Purifier Always Better?

No, a more expensive air purifier is not always better. Above $300, you pay for features that do not improve filtration: larger coverage area, smart home integration, premium design, or brand recognition. The filtration media itself, True HEPA H13, is the same at $150 and $600. The difference is the CADR capacity, noise engineering, and filter replacement cost, not the fundamental filtration mechanism.

The Coway AP-1512HH at $200 and the IQAir HealthPro Plus at $900 both use mechanical filtration to capture particles. The IQAir delivers higher CADR, covers a larger room, and uses HyperHEPA media rated to 0.003 microns. For a 200-square-foot bedroom, the practical difference in PM2.5 reduction between the two units is negligible. The IQAir justifies its price only in very large spaces or for users with severe chemical sensitivities who need the multi-stage gas-phase filtration.

For most home users in rooms under 400 square feet, a sub-$300 unit from a reputable brand with AHAM-certified CADR and CARB certification delivers the same air quality improvement as a premium unit at one-third to one-half the price. The money saved is better spent on a PM2.5 monitor to verify your air quality, which provides more actionable information than a more expensive purifier.

For most home users seeking clean air without overpaying, the Coway AP-1512HH at $200 delivers the best combination of verified smoke CADR, low noise, and affordable filter replacement in the sub-$300 category. The Winix 5500-2 is the better choice if pet odors or cooking smells are a primary concern. The Levoit Core 400S offers the best smart features and quietest operation. The Blueair Blue Pure 211+ provides the highest CADR for large rooms. Calculate your CADR requirement at your target ACH, match it to the closest unit, and verify the results with a PM2.5 monitor. Clean air is a measurement, not a feeling.