The Cutting-Edge Future of Indoor Air Quality Measurement

Posted on 04/25/2019

One of the often-cited challenges for air duct cleaners is testing or measuring indoor air contaminants. There’s the process of taking the air samples, then sending them off and awaiting the results. The waiting game has long been just another part of doing business. Now, imagine if you could walk into a building or home, conduct an instant particle count and profile and immediately identify what particles are in the space and the possible sources of those particles. Mark Hernandez, PhD, PE, professor of civil, environmental and architectural engineering at the University of Colorado in Boulder, has been conducting research with the technology to do just that.

About Mark
Hernandez’s research focuses not on how to clean air ducts, or even how to clean or purify indoor air, but how to assess the effects of cleaning “on the fly,” as he puts it. “What I’m researching focuses on the organic and microbial stuff we breathe every day, and that science is applied to the cleaning practice.”

Hernandez arrived in his field serendipitously on a quest to answer some critical questions about air quality. “I was trained as a wastewater treatment engineer,” he says. “For my PhD I worked on the microbiology of wastewater treatment and worked in sewage plants, which doesn’t sound very interesting, but it’s actually very interesting. Our cities generate billions of gallons of sewage daily, and the main thing responsible for the wastewater treatment process is microbes. Sewage is dangerous until you disinfect it.”

It was an innocent but important question from a plant worker that sparked Hernandez’s curiosity in aerosol disinfection. “You could see things — microbes — hovering in the air and someone at the plant asked me, ‘What am I breathing while I’m working here?’ I thought, ‘That’s a good question.’” Further interest in the role of air ducts and healthy buildings came after the events of 9/11 in New York City.

“After 9/11, the conversation focused on immune buildings,” said Hernandez. “If a bad guy lets something go near the air intake to a building, how can we design the circulation system of the building to protect those in the interior from biological and radiological attacks? We need systems that can sense, and then protect. That’s where the ducts come into play.”

Hernandez took all of his microbiology skills and applied that to ductwork. “What’s flowing through the duct and what’s stuck on the duct wall both matter — they’re both exposures,” he said. “Some stuff accumulates and sticks to the duct walls, while some breaks off and ends up in someone’s room. That material is made up of some things that are alive and some that are not, but they can all cause allergies or illness.” All of this led Hernandez to his latest research assessing particle load both pre- and post-cleaning. “It’s time to get the technology I’ve been using into the hands of air duct cleaners,” he said.

About the Technology
The technology Hernandez uses in his research is cytometry, commonly used in biotechnology to count and sort cells. Specifications for size, geometry and color are set, and a laser is used to process the sample by reflecting light off each cell in the sample and counting those that meet the set specifications. Previously, samples needed to be suspended in a stream of fluid, but Hernandez’s research uses a new generation of cytometers capable of measuring air.

“What’s especially interesting about this new generation of cytometers is that in addition to shining regular laser light, they now measure fluorescence,” said Hernandez. “That’s exciting because biology fluoresces— bacteria, fungi, viruses — different microbes have different fluorescent signatures. This new technology can detect those different signatures.” Hernandez’s research built a library of the fluorescent properties of different microbes. “I challenged this new generation of cytometers with all sorts of bad guys to find out their physical properties and identify them in real-time indoors,” he said.

That library has the potential to be game-changing for the air duct cleaning industry. NADCA members using the technology and utilizing the library of Hernandez’s research results will be able to answer some very specific questions that previously took time testing and waiting for results. “The technology allows technicians to more comprehensively characterize the outcome of a cleaning,” said Hernandez. “We can now answer, ‘If I cleaned something, did I lower the particle load? Did I lower the biological load?”

A Forum at NADCA
Hernandez was invited to speak at NADCA’s annual meeting by Mike White and Richard Lantz, who saw Hernandez present at another industry event. “His presentation was very interesting and definitely related to the work NADCA’s members are doing,” said White. “You have the ability to have the particulate identified upon your initial investigation, instantly. This really gives you a picture of what’s going on in that moment so you can begin to determine cause and effect.”

Hernandez’s session presented case studies from hospitals, Hernandez’s lab, and operating classrooms, and took attendees from the lab to the field. “Presenting about my lab is interesting because I can aerosolize anything I want in there — ragweed, tuberculosis — and I can sample and disinfect that air and see how that real-time technology affects that air.” The field study Hernandez presented discussed the HEPA filtration system in a hospital that was measured before and after the building went into operation, focusing on particle loading following occupation.

NADCA has a standard in place for its vacuum test for cleanliness verification, which this technology would support. “The technology would enhance the cleanliness verification process by allowing technicians to see if any airborne particulate is associated with the ventilation system,” said White. However, according to White, the real value is seen in its potential application in the initial investigation of IAQ.

Future Applications
While most of the new-generation cytometers are owned by larger franchises conducting industrial hygiene tests and academic institutions, Hernandez sees the potential for the technology to be in the hands of duct cleaning companies very soon. “Just like computers, the economy of scale will allow the machines to become smaller, cheaper and easier to calibrate,” he said. “They have a version on wheels, like a little suitcase. You can roll it into an environment and get representative samples in multiple rooms in a short amount of time.”

Hernandez hopes for large-scale adoption that would add to his database and allow users to search for specific conditions by context. “I could see building a database that allows us to see what’s normal in hospitals in the Southeast, or what’s normal for a wood frame house in New Jersey. We can get data for what’s normal and abnormal in different contexts and how cleaning affects particle loads. I see it hopefully being a routine monitoring tool, too, where the system would let us know that something isn’t normal in terms of particle loads. A basic particle counter can’t do that.”

While the research is making waves industry-wide, Hernandez credits his team for working diligently to transform what we know about measuring IAQ. “I have a core of very talented grad students and professional scientists who all share my vision,” he said. “We see the translational potential for monitoring an environment in ways we’re just starting to discover.”