Air Quality Monitor and Laser Particle Counter Reviews

Dust in Sunlight

Do you have an issue with pollution coming in from outside, or more commonly, inside your home?

“Allergy” can be triggered by many types and sizes of particulate and thousands of chemicals. What is perfect for seasonal pollen or mold allergy individuals may be unacceptable for borderline chemical sensitivity types. Strengthening your immune system is a lifetime task, and setting up your air quality defenses is a step in the right direction.

I recommend a thorough analysis of your needs and premises. Start with your macro view – freeway or industry close? Building age and use history? What’s the age and condition of your flooring (carpeting versus hardwood floors) and upholstery? Current or prior tobacco use? Natural gas appliances? Pets or animals on site? Particleboard? Air fresheners?

A particle counter and levels of formaldehyde/VOC are essential at the start.

Central HVAC systems, if dust loaded or moldy, will overwhelm any vacuuming/sterilization/air purifier, so incoming airflow quality and air changes, per hour, must be evaluated.

I would avoid treating carpets with anything that could possibly be considered toxic.

Many folks install an air purifier, set it on low in a too big room, and relax. Air purifiers must operate on high speeds, in confined spaces, to assure low particulate counts in health critical situations.

This may be too noisy, so a particle counter can be used to assure safe levels while managing noise.

Sensor Driven Air Purifier Reconsidered

When I first started reviewing air purifiers, I was really excited about the potential of automated, sensor driven room air cleaners. I felt that energy savings and feedback to the user, as subtle changes in air quality tripped the sensors, were worth the higher prices. As time went on, user feedback began to change my mind. Then I bought a laser particle counter and began measuring real-world performance of my air cleaners. I was shocked to find that sensor-driven air cleaners failed to deliver truly clean air.

Inexpensive electronic sensors are everywhere nowadays. High dollar applications, in industry and the military, spin off to produce very cheap imitations for mass-market products.

I run my particle counter every day in my office. At least one air purifier is also running. What I have found is that running the same air cleaner on middle or higher speeds, produces much lower particle counts than Auto Mode. Sustained high speed operation is the only way to obtain low counts. This increases the premium for quiet air cleaners, which ironically tend to be those equipped with sensors to start with. Sensors inexpensive enough to be added to room air cleaners just aren’t of high enough quality to match subtle variations in air quality. Air cleaners as cheap as $100 have been fitted with odor and/or dust sensors.


Particulate tends to be uniformly distributed in a room, and spike with foot traffic or a new source, maybe burnt toast. The result is high levels are required to trip sensors. By the time most automated air cleaners sense particulate, it has been slowly climbing for some time. Low cost particle sensors may change readings with humidity. There is an inverse-square law between particular levels and distance from the air cleaner, especially in the too-large room sizes commonly used to market air cleaners. After all, we are basing our room size recommendations on full-time top speed operation.

My $350 Dylos particle counter is the .5 micron version. It costs about $100 more than their 1.0 micron model. Dylos is the only laser particle sensor that measures down to the very small and extremely dangerous, PM 0.5.

I’m guessing that most automated air cleaners are equipped with 2.0 or larger sensors.

Why should we pay extra for well-sealed true-HEPA filters, capable of capturing .1 micron particulate, and then use 2.0 micron level to activate the air cleaner?

Just dropping the sensitivity of a handheld laser particle counter to .3 microns raises the price to $2,000+ range.

Measuring Odors

Odor sensors are very popular. Their antics make great conversation as the dog walks past and the lights turn red. But this is not really air purifying. The issue is not whether the air cleaner can react to a point source emission, but whether it can provide improved air quality long term.

Odor sensors can signal the existence of gas phase pollutants, but cannot measure their concentration or distinguish among triggers.

Gas molecules often diffuse from point sources but not always in close-proximity to the odor sensor.

A sensor can only detect contaminants in air that is close to the purifier. When the fan kicks in, air near the machine is cleaned and the fan slows down. But ambient air quality, often just a few feet from the air cleaner, has not improved enough to justify shutting down the fan.

Sensor Baseline Setting

Critical to auto mode operation is baseline setting. Instructions on baseline setting are hidden in that multilingual manual that many users will not read. Inexpensive air quality sensors require a number relative to the current reading for comparison. That number is the “baseline”. Most air cleaners reset the sensor baseline values each time they are plugged in. If the room is heavily contaminated to start with, the “intelligent” air purifier will think this is normal, using that setting to decide when to speed up.

I have found that running several air purifiers in a closed room until the particle count is low, then resetting baseline, will achieve the best baseline settings. But this is completely impractical, as the air cleaner cannot be moved to another room without losing the setting.

Auto Mode

Auto Mode operation, quietly idling the air cleaner, with little bursts of noise as particulate or molecular pollutant spike, is entertaining and comforting to users, but will never achieve the healthy indoor air quality which is the purpose of air purifiers.

My biggest concern is that users are given a false sense of security when the green lights stay on, while air quality is worse than it could be with a simple flick of a dial or button to a manual setting.

Buyers and owners of sensor-based automatic air cleaners should consider choosing frequent higher-speed manual operation for best air quality.

Investing in an air quality monitor or a laser particle counter is the only way to “guarantee” indoor air quality.

Air Quality and Laser Counter Reviews

Dylos DC 1100 Laser Air Quality Monitor Review

Awair Air Quality Monitor Review

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