# Can a ducted heat pump help keep wildfire smoke out of a Sacramento home? > How a ducted heat pump handles wildfire smoke in Sacramento: filters, airflow limits, fan settings, leaky returns and what an air handler replacement can fix. URL: https://tulesacramentoheatpump.com/guide/heat-pump-wildfire-smoke/ Learn Why a heat pump recirculates rather than ventilates, how filter rating and filter size trade off against the airflow a heat pump needs, which settings help on smoke days, and what an air handler replacement can fix. A ducted heat pump can help, mainly because it recirculates and filters the air already inside the house instead of drawing outdoor air in. How much it helps depends on the filter, on how much air the system moves through it, and on whether the ducts leak. On smoke days the settings matter as well: windows closed, outdoor-air devices off, and the fan running. [Tule Sacramento Heat Pump](https://tulesacramentoheatpump.com/) installs ducted heat pumps and replaces air handlers across the Sacramento region, through licensed and insured contractors. This guide explains the mechanisms without guessing at numbers, because filtration results depend on each house. Key takeaways - A heat pump moves heat through sealed lines; its outdoor unit brings no outside air indoors - A central return filter cleans all the air the system circulates, so filter choice and filter size decide how much smoke it catches - Denser filters resist airflow, and a heat pump needs enough airflow per ton to perform - Leaky return ducts in an attic or garage can draw unfiltered air in; Title 24 duct sealing reduces that - An air handler replacement is the moment to add a deeper filter cabinet or a larger return ## How smoke gets into a house Fine smoke particles ride in on air. A house exchanges air with the outdoors through: - open windows and doors - gaps around doors, windows, recessed lights and attic hatches - kitchen and bath exhaust fans, which pull replacement air in through those gaps - whole-house fans and evaporative coolers, which deliberately blow outdoor air through the house - return ducts in an attic or garage that leak, pulling in air from those spaces A ducted heat pump is not on that list. Its outdoor unit trades heat with outdoor air through a sealed refrigerant loop, and no outside air crosses into the duct system. ## Why recirculation helps The indoor blower pulls house air through the return grille and filter, across the indoor coil and back out the supply registers. Every pass through a good filter removes part of the fine particles. The more air that passes, the faster indoor levels drop, which is why fan time matters as much as filter quality. ### Compared with an evaporative cooler An evaporative cooler works by pulling outdoor air across wet pads and pushing it through the house, so on a smoky day it brings the smoke in with it. About 13% of SMUD households had one in the California Energy Commission’s 2019 survey. The [heat pump vs swamp cooler guide](https://tulesacramentoheatpump.com/guide/heat-pump-vs-swamp-cooler/) compares the two. ### Compared with ductless heads A ductless head has a fine screen that catches dust but not much fine smoke, and each room’s head treats only that room. The central filter in a ducted system is a real advantage here; the [ducted vs ductless guide](https://tulesacramentoheatpump.com/guide/ducted-vs-ductless-heat-pump/) covers the rest of the comparison. ## The filter tradeoff ### Rating MERV is the common scale for HVAC filters: higher ratings capture smaller particles. Wildfire smoke is mostly very fine particles, so a higher-rated filter catches much more of it than a basic one. ### Resistance Denser media also resists airflow. A heat pump depends on moving enough air: Title 24’s refrigerant charge check assumes at least 300 cfm per ton. Choke the airflow and the system loses capacity, the indoor coil can ice in summer, and in winter the thermostat leans on backup strips. Swapping a dense filter into a slot sized for a thin one can cause all of that. ### Surface area is the way around it A deeper filter, or a larger return with more filter area, spreads the same airflow over more media, so resistance stays low even at a higher rating. That is a physical change to the return or filter cabinet, which is easiest to make when the air handler is replaced. SMUD lists filtration and enlarged returns among the factors that change a heat pump project’s installed cost. > One-inch slots > > If your filter sits in a thin slot behind a single return grille, ask before moving to a much denser filter. A quick static pressure reading shows whether the system can take it. ## Settings for smoke days - **Close up.** Shut windows and doors; turn off the whole-house fan and any evaporative cooler. - **Run the fan.** Set the thermostat fan to on rather than auto so air keeps passing through the filter while the heat pump cycles. - **Use exhaust fans briefly.** Kitchen and bath fans pull outdoor air in through gaps; use them only as long as needed. - **Check the filter.** Smoke loads a filter faster than ordinary dust; change it after a long smoke event. - **Rinse the outdoor coil.** Once the air clears, wash ash and debris off the coil gently so it can breathe. A portable air cleaner in a bedroom can supplement the central system, especially at night when the system fan may be off. Plan better filtration into your heat pump Return size, filter depth and blower capacity are sized together, so a better filter does not cost airflow. ## Ducts decide how much air bypasses the filter Return ducts run under negative pressure, so any leak pulls air in from wherever it passes: a hot, dusty attic or a garage. That air reaches the coil and the rooms without going through the filter. On every change-out, Title 24 has the installer seal the connected ducts and an ECC-Rater test them, with a target of 10% total leakage or 7% leakage to the outside, and 6% where ducts or equipment sit in a garage. Tighter returns mean more of the house’s air passes the filter. [Heat pump ductwork](https://tulesacramentoheatpump.com/heat-pump-ductwork/) covers sealing and replacement. ## What an air handler replacement can fix When the indoor unit is replaced, the return and filter arrangement is open anyway. That is the time to: - add a deeper filter cabinet at the air handler or a larger return grille with a deeper filter - correct an undersized return that limited airflow - choose a variable-speed blower that can run continuously at low speed with less energy - seal the return plenum and the connections that leak most [Heat pump air handler replacement](https://tulesacramentoheatpump.com/heat-pump-air-handler-replacement/) explains when the indoor unit needs to change and what else the job involves. ## Living with it between smoke seasons A filter that suits smoke season also suits the rest of the year if the system was designed for it. Check it on a regular schedule, keep plants and fences clear of the outdoor unit, and keep the condensate drain clear. [Heat pump maintenance](https://tulesacramentoheatpump.com/heat-pump-maintenance/) covers a yearly check, and the [lifespan guide](https://tulesacramentoheatpump.com/guide/heat-pump-lifespan/) explains how airflow and filters affect service life. The [installation process guide](https://tulesacramentoheatpump.com/guide/heat-pump-installation-process/) shows where airflow is set during commissioning. To plan filtration with a new system, call (916) 516-1454 or [request an estimate](https://tulesacramentoheatpump.com/contact/). ## Questions about this guide ### Does a heat pump's outdoor unit pull smoky air into the house? No. The outdoor unit only moves heat through sealed refrigerant lines; no outdoor air passes from it into the house. Smoke gets in through open windows, gaps in the building, exhaust fans that draw makeup air, evaporative coolers, and leaky return ducts in an attic or garage. The outdoor coil can collect ash, which is worth rinsing off once the smoke clears. ### Should the system fan run all the time on smoke days? Running the fan continuously sends the house's air through the filter many more times, which lowers indoor particle levels faster, so it usually helps while smoke lingers. It uses some extra electricity, more on an older fixed-speed blower than on a variable-speed one. Keep windows closed and turn off any whole-house fan or evaporative cooler at the same time. ### Can a higher-rated filter hurt a heat pump? It can, if the filter slot is small. Denser media catches finer smoke particles but resists airflow more, and a heat pump needs enough airflow per ton to reach its capacity, keep its coil from icing and avoid leaning on backup heat. A deeper filter with more surface area, or a larger return, lets a better filter work without starving the system. Want this answered for your house? Call with your current system, the rooms that bother you and your ZIP code. ## Related service Air handler replacement A new indoor fan and coil cabinet matched to the outdoor unit, with the drain, filter, backup heat and duct test done to Title 24. ## More guides - Decision Guide [Should a Sacramento home get a ducted or a ductless heat pump?](https://tulesacramentoheatpump.com/guide/ducted-vs-ductless-heat-pump/)How the two systems get heat into each room, what the existing ducts decide, what SMUD's rebate-program data shows about cost, and where a ductless system is the better fit. - Learn [Where should a heat pump's outdoor unit go, and how do you keep it quiet?](https://tulesacramentoheatpump.com/guide/heat-pump-placement-noise/)How location affects airflow, drainage, service access and sound, what the City of Sacramento and Roseville permits allow when a unit moves, and the installation details that decide how loud a heat pump is. - Learn [How long do heat pumps last in Sacramento?](https://tulesacramentoheatpump.com/guide/heat-pump-lifespan/)What wears a heat pump out, why a system that heats and cools all year builds hours faster, which installation details protect it, and how to decide between another repair and a replacement. - Decision Guide [Should a Sacramento home replace its swamp cooler with a heat pump?](https://tulesacramentoheatpump.com/guide/heat-pump-vs-swamp-cooler/)Evaporative coolers suit the valley's dry summers, up to a point. This guide compares them with a ducted heat pump on cooling limits, smoke days, winter heating, running cost and the duct and roof work a switch can involve. - Learn [What happens during a heat pump installation, step by step?](https://tulesacramentoheatpump.com/guide/heat-pump-installation-process/)The order a ducted heat pump job follows from the first look at the house to the final inspection, what each step depends on, and where Title 24 testing and the permit fit in.