Owning an air purifier can be an excellent decision as we spend most of the time indoor. As EPA says, indoor air can be two to five times more polluted than outside air. An air purifier plays a vital role in improving indoor air quality. Almost half of the US families own an air purifier nowadays. Here we are going to talk about indoor air pollutants, technologies of air cleaning and discussing 10 key points you need to consider to choose the right air purifier based on EPA guidelines.
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What’s in the indoor air: Indoor air comprises of two types of pollutants: particulates and gases. Pollen, pet dander, house dust, dust mites, mold spores are particulate pollutants and also known as particulate matter. VOCs from paint and other household items and all types of odors are gaseous pollutants. Smoke contains both particles and gases. Indoor air pollutants categorize as PM10, PM2.5, and PM1 by their sizes. PM2.5 is the most common and fine airborne pollutants. PM10 is heavy, and PM1 is ultrafine pollutants.
Conventional Air Purifying Technologies:
| Technology | Filter type | Target Pollutants | Advantages | Disadvantages |
| Fibrous Media Filter | True-HEPA, HEPA-Type, HEPA-like | particles | Safe to use for all, highly effective, suggests by EPA | Need to replace filters frequently, costly |
| Absorbent Media | Activated carbon/charcoal, zeolite | gases | Excellent for odor, VOCs. Suggests by EPA | Low filter life, costly |
| ESP | Electronic, permanent washable filter | particles | Permanent filter, low cost | Not suitable for asthma or breathing conditions, produce ozone, less effective |
| Ionizer | Release negative ion into the air | particles | Fetterless, small in size | Produce a little amount of ozone, do not eradicate particles from the room |
| Plasma wave | Create a plasma wave to break gases | gases | Very good at removing odors and gases | Formaldehyde or other bi-products might produce |
| UV-C | Ultraviolet light destroys microorganism cells, works as an air sanitizer. | Microorganisms | Excellent for destroying dust mites, bacteria, mold spores, and viruses | Don’t remove entirely from the air |
How to Choose the Right Air Purifier:
1. Types of Air Purifier
Portable indoor air purifiers are two types: mechanical and electronic. The mechanical air purifier uses one or several layers of mesh-like fibrous filters and a fan to pull or push the air through the filters to purify the air. Popular electronic air purifications technologies are electrostatic precipitation (ESP), ionizer, UV-C, plasma-wave, and intentional ozone generator.
HEPA filter air purifiers are considered as a gold standard of mechanical air purifiers. HEPA or High-Efficiency Particulate Air filters can remove 99.97% of particle pollutants that are sized 0.3 microns in diameter. True HEPA air purifiers are highly effective against particle pollutants, and it is suitable for everyone. Also, these are relatively costly for both one-time purchase and maintenance.
Electronic air purifiers use electric filtration techniques to purify the air. ESP filters are permanent and washable. Ionizer released negative ion and make the airborne pollutants sticky, which ultimately fall to the ground, furniture, or stick to the walls and ceilings. Ozone generators produce ozone, which reacts with VOCs and gases chemically to neutralize them. UV-C lights destroy airborne organisms like dust mites, mold spores, and bacteria. Plasmawave neutralizes odorous gases and VOCs.
Bottom line: EPA suggests to use a True HEPA air purifier that has a high MERV rating (16 or higher). There are also HEPA-type or HEPA-like air purifiers that have lower efficiency than True-HEPA. You can select them if you are on a budget. ESP or ionizers air purifiers have lower effectiveness than HEPA, and they produce a small amount of ozone as a bi-product. You can select them if the ozone production rate is at a safe level. Don’t choose electronic air purifiers if someone has asthma or breathing issue at home. Intentional ozone generators are not suggested for homes.
2. Activated Carbon Filter (Gas & Odor Filter)
Most of the modern air purifiers have an additional activated carbon filter. Activated carbon, also is known as an activated charcoal filter, uses activated carbon substances to absorb odorous gases and VOCs from the air. HEPA filters, Ionizers, or ESPs are good for particle removal but not suitable for removing harmful gases. Activated carbon filter, plasma-wave, and ozone generators are used to remove gases from the air. If odor, VOCs, and chemicals are your primary or secondary concern, then you need to select an air purifier that is equipped with an activated carbon filter. These filters got saturated quickly and need to replace earlier than the HEPA filters.
Bottom line: For Smoke, VOCs, gases, and chemicals, select an air purifier with a thick layer of an activated carbon filter. An additional plasma-wave filter will help to increase effectiveness.
3. Clean Air Delivery Rate or CADR
The CADR ratings are the most significant indicator to understand the performance of an air purifier. Filtration techniques indicate the effectiveness, while CADR indicates the efficiency of an air purifier. CADR or clean air delivery rate expressed as cubic feet per minute, an industry-standard introduced by AHAM, and now even recognized by authorities. AHAM also verify and give CADR ratings for air purifier. They test air purifiers for three types of pollutants, which are Pollen, Dust, and Smoke. The high CADR means a greater airflow rate, which is better. You need to select the CADR according to your room size and the conditions of the air. Some manufacturers test air purifiers by themselves. CADR is also expressed as a cubic meter per hour by some manufacturers. A CADR value of 100 cubic meter per hour is equivalent to 69 cubic feet per min. So, be careful when you check the CADR value.
Bottom line: Higher CADR value means faster cleaning comparatively. But higher CADR value doesn’t mean the higher effectiveness. Look at the physical unit cfm or cmh and select the CADR according to room size and ACH. For a 150 sq ft room, select CADR 100-120 cfm, for 300 sq ft room select CADR 200-220 cfm, for a large 400-500 sq ft room select the CADR 270-330 cfm. Remember, the given CADR value is for the highest fan speed.
4. Room Size Calculation with ACH
You choose a top CADR air purifier, then what? You also have to consider the room size based on ACH or Air Changes Per Hour. An air purifier can clean the air from any sized of closed space (think of a big hall room), but you wouldn’t give it infinite time to clean, right? Here comes the Air Changes Per Hour, also known as ACH or ACPH. It defines how fast an air purifier can clean the air from a specific sized room. ACH depends on room size and air purifier’s CADR rating. For example, five air changes per hour mean it can clean the air from the entire room five times in an hour, or it takes 12 minutes to clean the whole volume of air from that room. For allergy or smoky air condition, you need to select the ACH higher. It is suggested to choose the minimum ACH 5 when calculating the room size or CADR.
Bottom line: Calculate your CADR based on your preferred ACH value. For smoky air or higher air pollution, select the minimum ACH 8-10 to get the most from the air purifier.
5. Noise Profile
Sometimes you need to operate the air purifier all night at the bedroom. Or you might want to use it in your reading room or baby’s room. A loud air purifier could bother you or baby. For this instance, you have to consider the noise profile of an air purifier. Typically air purifiers noise lies on 25 dB to 60 dB at different fan speed settings. For a pleasant sound, the minimum noise should be 20-25 dB on the lowest fan speed and 40-45 dB on the highest fan speed. A 40 (decibel) dB noise is equivalent to whispering noise.
Bottom line: When checking on the noise profile of an air purifier, consider the noise level at its maximum fan speed. Because of the lowest mode, you will get a shallow air flow rate or reduced efficiency.
6. Built-in Air Quality Sensor
Most of the modern air purifiers have a built-in air quality sensor. It has two benefits: you can check your indoor air quality status in real-time, and the number two is the air purifier adjusts its fan speed based on the real-time air quality reading. The most common air quality sensor is a particulate (PM) sensor, and they show the indoor air quality status as a color indicator or by PM2.5 count. Some air purifier uses VOCs sensor, and they only detect VOCs and gases. A few air purifiers use both particulate and VOCs sensor to measure indoor air quality.
Bottom line: Air quality sensor is helpful in terms of energy savings and user satisfaction.
7. Price and Maintenance Cost
The price of the most popular portable indoor air purifier ranges from $50 to $1000 on average. HEPA air purifiers are relatively costly than electronic (ESP) air purifiers, and their annual filter replacement cost ranges from $20 to $150 on average. We can categorize air purifiers in 4 categories based on their prices:
| Category | Suitable for | Price |
| Low | Desktop-grade personal use | $50 – $100 |
| Mid-range | Small room <150 sq ft | $100 – $200 |
| Upper mid-range | Medium room <400 sq ft | $200 – $500 |
| Upper-range | Large room, medical-grade filtration | $500 – $1000 |
Bottom line: Air purifiers price depends on filter type, additional filters, capacity, and features. Some air purifier doesn’t cost much, but their replacement filter price is above average. Don’t forget to calculate the relative annual filter replacement cost when you select an air purifier.
8. Size and Portability
Different air purifiers use different mechanisms for air intake and output for fresh air. Air purifiers come in different sizes and shapes. Some are flat and can be used against walls and also mountable on the wall. Most air purifiers have to be kept away from walls. Many air purifiers have a carry handle and wheels to move between rooms. Some are super portable, and some are bulky, and also they don’t have wheels.
Bottom line: At first, decide where you want to use the air purifier in your house and how much portability do you need. Then select your air purifier according to your plan.
9. Features & Certifications
Today’s air purifiers are feature-rich. The most common features are the filter-life indicator, timer, and sleep mode. Some additional features like child lock, remote control, Wi-Fi or Bluetooth connectivity, and auto-activated night mode are available on upper mid-range to high range air purifiers. Some air purifiers are Alexa and Google Home enabled so you can control them by voice.
Bottom line: Check the features are available that you need badly when you are selecting an air purifier.
10. Certifications & Standards:
CADR ratings by Association of Home Appliance Manufacturers (AHAM) are the most common certification among the indoor air purifiers. CADR by AHAM also the most accepted standard for selecting an air purifier. Many manufacturers listed their self-tested CADR.
Some air purifiers come with Energy Star seal, and those are energy efficient. It will be helpful for those who need to run the air purifier for 24 hours.
Another check the air purifier is CARB compliant for ozone-free air purifiers in California. If your device has some ozone-generating technologies, then you must check it.
Bottom line: CADR certifications by AHAM is significant but not necessary.
Although an air purifier cannot improve your indoor air quality alone, it is an excellent device that plays a vital role in improving indoor air quality. For choosing the right air purifier, this insightful guide will help you to bring the best air purifier to your home.
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