Episode 676: R Subramanian, PhD - An International IAQ Perspective & Low Cost Monitor Review

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Episode 676: R Subramanian, PhD - An International IAQ Perspective & Low Cost Monitor Review

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Re: Episode 676: R Subramanian, PhD - An International IAQ Perspective & Low Cost Monitor Review

Post by CliffZ »

Episode 676| September 23, 2022 | 12:00 PM EST

R. Subramanian, PhD, An International IAQ Perspective & Low Cost Monitor Review

Nuggets mined from today’s episode:

How did you become interested in monitoring devices? Dr. Subramanian began researching air quality field in 2003 while at Carnegie Mellon University. At that time an ozone monitoring device cost $10K and a small particle monitoring device <2.5PM cost $20K-$30K.
In 2013-2014 while again at Carnegie Mellon he was involved in a project to map air quality in and around Pittsburgh, PA. He needed to select between the two available options: mobile IAQ lab or dedicated monitoring sites. The mobile lab was able to monitor one site at a time. Because Pittsburgh has many hills and valleys; he knew that potentially 30-50 monitoring sites would be needed to obtain the needed data. He sought to use low-cost monitors which resulted in development of RAMP system (Realtime. Affordable, Multi-Pollutant) through a combination of industry and academia. SenSevere, LLC was the industry partner. Financial support for this program from the USEPA and the Heinz Endowment. The number of original monitoring sites has been scaled back to 30. He estimates that the RAMP system is in the $4K range.

How are airborne particles counted and what if anything effects their accuracy? Particles are counted with a light scattering device. High humidity can fool the device into overcounting.

Do the terms precise and accurate mean the same thing? No, accurate refers to calibration. Precise refers to consistency 10 out of 10 sensors all read the same. Precise devices are useful in determining trends.

Are you familiar with Linda Wigington and ROCIS (Reducing Outdoor Contaminants in Indoor Spaces)? Yes, he is familiar with Linda and the great work her organization does in: raising awareness, providing training, guidance and contaminant reduction interventions.

How did sensors get to be low cost? Market demand, competition, mass manufacturing, reproducibility and economies of scale have driven down sensor costs. The surge in low-cost sensor development is driven by sensors for HVAC which are precise and low-cost. Many sensors in the cost range between $12-$50

Where are quality low cost sensors made? Quality low-cost sensors are made in: China, Switzerland, Germany, US, etc. Low-cost senor manufacturers include: Honeywell, Bosch, Sensirion, Plantower, etc.
• Core sensor options include: Plantower and Sensirion
• The photo ion sensors in costly GC/Mass Spectrometers samplers cost around $600.

Is particulate air pollution geographically consistent? No, particulate air pollution can vary widely. It is recommended to calibrate sensors locally. Note: Plantower sensors are calibrated to a city in China not to cities in the US.

Particle counter sensors may have significant deficiencies. Particle counters count small particles (1 micron) more accurately than larger particles (10 micron). High humidity causes sensors to overcount.

Is there a universally recognized standard or rating that we should be using? No, its like the wild, wild west. 3rd party product certification is costly and may take 2-3 years. It’s likely that the product would be outdated by the time it was certified.
http://www.aqmd.gov/aq-spec established the Air Quality Sensor Performance Evaluation Center (AQ-SPEC) program. The AQ-SPEC program aims at performing a thorough characterization of currently available “low-cost” sensors under ambient (field) and controlled (laboratory) conditions.

Wildfires are a big problem in the US and in other countries. What role do you envision sensors having in post wildfire cleanup? RAMP won the wildfire challenge.
https://www.epa.gov/sciencematters/wild ... -measuring Having sensors both indoors and outdoors can provide data on building envelope air leakage pathways.

How often do sensors need to be cleaned and how are sensors cleaned? Particle counting often last 3-5 years. Can be “air washed” with canned air. Recommends that low-cost sensors be considered disposable.

Random Comments:

• Likes off the shelf products. When he finds a product he likes he’ll buy several to evaluate preciseness.
• Recommends sensors be placed where there is free flowing: in breathing zone, kitchens, HVAC cold air returns.
• Opined that the PurpleAir sensor is genius.
• Opined Particles Plus makes good particle counters.
• Opined TSI is the world leader in optical particle counters


• Knowing is power
• Sensors will continue to improve
• Sensors make it easy for people to track pollutions
• Know the limits of the sensor
• Dr. Submaranian shares his knowledge and interest in low-cost sensors on Twitter and is considering writing a book on the subject.

Z-Man signing off
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Re: Episode 676: R Subramanian, PhD - An International IAQ Perspective & Low Cost Monitor Review

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Name the company credited with developing the first portable device for sensing a toxic gas during mining operations?
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Re: Episode 676: R Subramanian, PhD - An International IAQ Perspective & Low Cost Monitor Review

Post by RadioJoe »

Glad I found Dr. Subramanian on Twitter. I have seen his posts for some time and when he posted about possibly writing a book on low cost monitors I had to try and get him. Little did I know that he got his PhD at CMU in IAQ Radio's hometown of Pittsburgh, PA. He is currently working in Doha, Qatar and brought a wealth of information to our audience.

My key takeaway is that low cost monitors are generally precise but not necessarily accurate. So the key is to know this and use them to give you trends more than exact numbers. I also found it interesting how much humidity can affect the particle counter sensors in the low cost monitors.

It was also very interesting to hear his perspective on worldwide IAQ issues particularly on how things are looked at in the middle east and Africa.

Thanks Subu!!
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