Wildfire smoke season: IAQ calls and filtration

Why smoke season brings HVAC calls

When wildfire smoke drifts over a region, phones at HVAC companies change tone. Customers who never thought about their filter want to know whether their system is protecting them, which filter to buy, whether to run the fan and whether they need an air purifier. Some calls come from areas hundreds of miles from the fire, because smoke travels far.

These are good calls to get. They come from people who trust you, they can be answered quickly, and they often lead to useful work: filter upgrades, return and cabinet changes, duct sealing, portable air cleaner advice and maintenance agreements. They also come with a responsibility to give accurate advice and avoid health claims you cannot support.

Who actually has central filtration

In the 2020 Residential Energy Consumption Survey, 88% of US households used air conditioning^[3], and two-thirds used central AC or a central heat pump as their main equipment^[4]. That leaves many homes with window units, mini-splits or no cooling at all. AC use is highest in the South at 93% and the Midwest at 92%, and lowest in the West at 73%^[2], a region that includes many of the places most often affected by wildfire smoke.

So the right advice depends on the home. For a house with a central forced-air system, the filter and the fan settings matter most. For a house without one, portable air cleaners do most of the work.

What EPA advises homeowners

• Choose a high-efficiency HVAC filter, such as MERV 13, or as high a rating as the system fan and filter slot can accommodate^[1].
• Make sure the filter fits snugly so air does not leak around it, and do not bend or crush a filter to make it fit^[1].
• If the system has a fresh air intake, close it or set the system to recirculate during smoke events^[1].
• Keep extra filters on hand and plan to replace them more often than usual during heavy smoke^[1].
• Use a portable air cleaner sized for the room, alone or alongside HVAC filtration^[1].
• When air quality improves, air the house out and run kitchen and bathroom exhaust fans^[1].

EPA also says homeowners may need an HVAC professional to find the highest-efficiency filter their system can take^[1]. That is the core of a smoke-season service call.

Customer questions and honest answers

Checking whether a system can take MERV 13

1. 01

   Measure the filter slot

   Note the nominal size and depth. Thin one-inch slots limit options; deeper media cabinets usually allow higher-efficiency filters with less resistance.

2. 02

   Check for bypass

   Look for gaps around the filter rack and missing covers. A high-rated filter with air leaking around it does little.

3. 03

   Measure static pressure

   Test total external static pressure with the current filter and compare it with the equipment's rated limits. This tells you whether there is room for a more restrictive filter.

4. 04

   Assess the return side

   Undersized returns are common. Adding return area or a second filter grille can make higher-efficiency filtration workable.

5. 05

   Recommend in writing

   Give the customer the highest filter rating the system can handle as it stands, and any changes that would allow better filtration, with prices.

Installation quality affects everything else. ENERGY STAR notes that improper installation can reduce HVAC system efficiency by up to 30%^[5]. A smoke-season visit that finds a leaking return or a poorly fitted filter rack is as valuable as the filter itself.

Fresh air intakes, ventilators and evaporative coolers

Systems that bring in outside air need specific advice. Show customers where the fresh air damper is and how to close it, or how to set a ventilator to recirculate or off during smoke. Evaporative coolers pull in large volumes of outside air. For a cooler that is safely accessible, EPA suggests completely covering the outside air intakes with 4-inch-thick MERV 13 furnace filters, which may need replacing often^[1]. Leave written instructions near the equipment, because the customer will need them again the next time smoke arrives and may not remember what the technician showed them.

Homes without central systems

For homes with window units, ductless systems or no cooling, portable air cleaners are often the main defense. Advise customers to size the unit to the room using its clean air delivery rate, to focus on a bedroom where they spend the most hours, and to keep doors and windows closed while it runs. Check whether ductless indoor units have washable filters that need cleaning more often during smoke. For window units, check the seals around the unit and any fresh air vent setting.

Stocking for smoke season

• MERV 13 filters in the sizes you install most, including deeper media sizes.
• Filter racks, cabinet kits and return grilles for quick upgrades.
• Gasket and sealing materials to close filter bypass gaps.
• Static pressure test kits for every service truck.
• A short list of portable air cleaner models and sizes you are comfortable recommending.
• Printed leave-behind instructions for recirculate settings and filter changes.

What the office says on smoke days

Avoid health promises. Say what a filter does, which is remove particles from air passing through it, and let customers with health concerns talk to their doctor. Heating and cooling already account for nearly half of the energy used in a home^[6], so if running the fan more often will raise energy use, say so.

Example: a smoke-season service package

Example (fictional): an HVAC company in a western metro sees smoke-related calls every late summer. It creates a fixed-scope air quality visit: filter slot and bypass check, static pressure test, fresh air intake demonstration, filter upgrade to the highest suitable rating and a written report. When smoke arrives, the office offers the visit to callers and to maintenance agreement customers first. The company keeps filters in stock for the sizes it sees most and quotes media cabinets and return upgrades for systems that cannot take a better filter as installed.

Turning one call into a long-term customer

Smoke-season callers are often new to your company. Many have never had their system serviced and do not know its age, filter size or settings. Use the visit to build a full record: equipment model and age, filter size and rating, static pressure readings, return and duct condition and the fresh air setup. Give the customer a copy. Offer a maintenance agreement that includes filter checks before the usual smoke months, and a reminder when smoke is forecast. A customer who received clear, honest advice during a stressful week is likely to call you first for repairs and replacement later.

After the smoke clears

Follow up when air quality improves. Remind customers to replace heavily loaded filters, reopen fresh air intakes and return ventilators to normal settings. For agreement customers, check coils and blower wheels at the next visit, since heavy loading can show up there. Record which customers bought upgrades and which declined, and contact them before the next smoke season with a short reminder and an offer to recheck their system. For planning staffing around smoke and heat, see weather-based marketing and staffing.