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Tech Tips:

As a technician, you most likely know some customers who still have an oldie thermostat (you know, those old mercury bulb things, like the round Honeywell CT87 and such). Keep in mind that those usually have an adjustable heat anticipator. If you’re newer in the field, you may not have seen or worked with those […]

How “Hot” Does That Get?

I got in one of these tiny torches the other day to experiment with brazing aluminum in tight spots, and one of the techs walked in and asked, “What type of torch is that?” I answered, “It's oxy/acetylene.” He picked it up and looked at it a bit, then asked, “Does that get hot enough […]

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HVAC School – For Techs, By Techs

Real training for HVAC ( Heating, Ventilation, Air Conditioning and Refrigeration) Technicians. Including recorded tech training, interviews, diagnostics and general conversations about the trade.

In this episode of the HVAC School Podcast, Bryan sits down with Kelsey Hei and Andy Fox from 3M Filtrete to pull back the curtain on what really goes into a quality air filter. Most homeowners — and even some contractors — think of air filters as simple screens that catch dust, but as this episode makes clear, modern filter technology is anything but simple. From proprietary nonwoven fiber structures to electrostatic charging that turns fibers into “magnets” for microscopic particles, the science behind a great air filter is both fascinating and critically important for equipment health and the air we breathe every day.

The conversation digs deep into why MERV 13 has become the gold standard recommendation from organizations like the EPA and CDC — especially in the wake of COVID-19 and worsening wildfire seasons across the country. While higher MERV ratings deliver better particle capture, they can also mean higher pressure drop, which strains HVAC equipment. This is where Filtrete’s MPR 1900 filter stands out: it achieves MERV 13 performance while maintaining a pressure drop comparable to most MERV 8 filters — roughly half that of leading competitors. That balance between filtration efficiency and airflow resistance is something 3M has spent over 35 years engineering.

One of the most compelling segments focuses on real-world testing. Rather than relying solely on lab data, 3M runs extensive in-home studies — placing filters in dozens of homes during Minnesota winters, then retrieving and analyzing them to measure real-life efficiency and pressure drop. This commitment to real-world validation ensures Filtrete’s claims hold up in the messy, variable conditions of actual homes, not just controlled lab environments. Bryan and the guests also discuss how overloaded or collapsed filters can cause serious equipment issues, including frozen coils and system shutdowns in extreme cases — underscoring why filter quality and regular replacement matter enormously.

The episode wraps with practical advice for contractors and homeowners alike: if you’re installing a new system, push for a four- or five-inch filter slot to maximize surface area, lower ongoing pressure drop, and extend filter life. For existing one-inch slots, the MPR 1900 is the top pick. The Filtrete Smart App is also highlighted as a handy tool for setting filter change reminders and monitoring local air quality — making it easier than ever for consumers to stay on top of their indoor air health.

Topics Covered

· 3M Filtrete’s history — 35+ years of indoor air quality innovation, owning the full manufacturing value chain from raw fiber to finished filter

· The three pillars of air filter design — Efficiency, pressure drop, and air filter lifetime — and how they must be balanced

· Nonwoven media explained — Why random fiber orientation captures particles more effectively than woven fabrics

· Electrostatic charging technology — How fibers are engineered to attract and trap microscopic particles

· Charge stability over time — Shelf life testing and real-world in-home studies to verify long-term performance

· Why MERV 13 matters — EPA, CDC, and ASHRAE recommendations; effectiveness against bacteria, viruses, allergens, and wildfire smoke

· Pressure drop and airflow — How high-resistance air filters strain equipment, raise energy bills, and can cause system failures

· MPR 1900 spotlight — MERV 13 filtration at MERV 8 pressure drop, with publicly available data through the California Energy Commission

· California Energy Commission database — Publicly available pressure drop and efficiency data on every filter sold in the U.S.

· Pleats and surface area — Why having more pleats equals better dust-holding capacity and a longer filter life

· Frame strength and bypass prevention — How structural integrity affects real-world performance over the filter’s lifespan

· MPR rating system explained — Microparticle Performance Rating: Filtrete’s system focused on capturing the smallest, hardest-to-catch particles

· Exceeding ASHRAE minimums — Filtrete’s MERV 11, 12, and 13 filters all capture significantly more fine particles than the minimum standard requires

· One-inch vs. four/five-inch filters — Why thicker filters are ideal for new installs and how to maximize one-inch slot performance

· Energy consumption impact — How pressure drop affects fan wattage, system efficiency, and real annual utility costs

· The Filtrete Smart App — Set filter change reminders at 30/60/90 days, store filter sizes, and get local air quality alerts

Learn more about Filtrete’s air filters at filtrete.com or download the Filtrete Smart App on your Android or iOS smartphone.

Have a question that you want us to answer on the podcast? Submit your questions at https://www.speakpipe.com/hvacschool.

Purchase your tickets or learn more about the 8th Annual HVACR Training Symposium at https://hvacrschool.com/symposium.

Subscribe to our podcast on your iPhone or Android.

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Check out our handy calculators here or on the HVAC School Mobile App for Apple and Android.

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Tech Tips:

Users with Tag #heat

To continue you need to agree to our terms.

The HVAC School site, podcast and tech tips made possible by generous support from

The HVAC School site, podcast and tech tips
made possible by generous support from