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- Smoke & the Wildland Edge
What a heating and air contractor can honestly do about smoke.
A narrower list than the marketing suggests, and a genuinely useful one once you know where the boundary is. This page is that boundary, written down.
The one sentence that matters.
A central system can clean the air inside a closed house. It cannot seal a building, and anybody who tells you otherwise is selling you something.
Almost every disappointment we get called about follows from confusing those two things. A household buys a filtration upgrade, a smoke event arrives, the house still smells of smoke, and the conclusion is that the equipment failed.
It did not. It filtered the air that passed through it, which is all it was ever able to do. The smoke came in through the gaps — around doors, through a sliding door track, down a chimney, through a bathroom exhaust with a damper that has not closed properly since 2009, and through the sheer volume of air that moves in and out of an ordinary leaky house every hour.
So this page is in two halves: what we can genuinely improve, and what belongs to the building rather than to us.
What we can genuinely improve.
- Filter area
- More surface, not more densityA filter has two jobs that pull against each other: catching particles and letting air through. The right answer for a smoky valley is usually a larger filter — a deeper housing, or a second return with its own filter — rather than a thicker one jammed into the slot you already have.
- The blower
- It has to be able to push through whatever you fitBefore we change a filter specification we check what the system can actually move. Fitting a much denser filter to a blower that cannot handle it means less air, worse cooling, and in a bad case an iced indoor coil. This is the most common self-inflicted problem we see here.
- Duct leakage
- Leaking return duct pulls attic air into the houseAnd during a smoke event the attic is full of exactly what you are trying to keep out. Sealing the return side is one of the highest-value smoke jobs in the building and it is invisible, so nobody sells it.
- Fan circulation
- Running the fan on its own is useful, once the house is closedIt keeps air moving through the filter instead of sitting still. It is free, it is already in your thermostat, and most people do not know it is there.
- Outside-air intakes
- Good most of the year, bad in SeptemberSome systems here have a fresh-air intake fitted for ventilation. It should be closeable, and you should know where the control is. An intake nobody can shut is a pipe into the house on the worst days of the year.
What belongs to the building.
We will point all of this out. We do not sell any of it, and that is precisely why we are worth listening to on it.
- Weatherstripping and door sweeps. The cheapest smoke improvement in most houses, by a wide margin.
- Sliding door tracks. An older slider can leak more than a window left open a crack, and nothing about it looks wrong.
- The fireplace damper. A chimney is a purpose-built hole in the roof. Closing it properly is free.
- Exhaust fan dampers. Bathroom and kitchen fans have flaps that stop closing after a decade of lint.
- The ceiling plane. Recessed lights, duct boots and wiring penetrations connect the attic to the rooms below. We seal the ones we can reach while we are up there.
- Everything outside. Roof, siding, decking, windows, clearance around the structure. Not ours, and not something a vent replacement substitutes for.
Embers go where air goes.
An attic vent is a designed opening in a building. That is its job, and it is also the problem.
Wind-blown embers travel well ahead of a fire front, and an opening that lets air in will let them in too. Construction rules for wildland-urban interface fire areas address that directly, including vents that are built and listed to resist ember entry. A great many properties around here sit inside such an area.
What we will not do is tell you what applies to your house from memory. These requirements have been revised more than once, and what governs a particular job depends on the address, the assessed hazard area and the scope of work. We check what is current at the point of pulling the permit and we tell you what it means before you choose anything.
What we will do is the work itself: replacing vents with listed ember-resistant vents where that is what the job calls for, correcting intake and exhaust balance, and sealing the penetrations through the ceiling plane that connect the attic to the rooms below.
One honest caveat
Vent work is one detail on one part of the building. It is a worthwhile detail and it is the part we are already in. It is not home hardening, it does not substitute for clearance around the structure, and we will not describe it as making a house safe. Anyone who does is overselling a $40 component.
A smoke event, in order.
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Close the house
Windows, doors, the fireplace damper. Switch off any whole-house fan or outside-air intake. This single step does more than any equipment you own.
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Run the fan
Set the thermostat fan to On rather than Auto so air keeps moving through the filter even when the system is not cooling.
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Pick one room
Choose a bedroom, close it, and put a portable air cleaner in it. Cleaning one room properly beats failing to clean a whole house, and it is where people actually spend the night.
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Change the filter after
A filter that has worked through a smoke event is loaded. Leaving it in restricts the system for the rest of the season, and this is the one job we would rather you just did yourself.
Four things we will not sell you
- Duct cleaning as a smoke remedy. In most houses it does not fix the complaint that prompted the call.
- Ozone generators. Not in an occupied house. Not for smoke. Not at all.
- An in-duct gadget as a substitute for filter area. If the filtration is undersized, fixing the filtration is the fix.
- A percentage. No claim about how much cleaner your house will be. We cannot know it and neither can anyone else quoting you one.
Asked once people have read this far.
Should I run the air conditioning during a smoke event?
Yes, if the house needs cooling — a normal central system recirculates indoor air through the filter rather than drawing in outside air, so running it is helpful rather than harmful. The exceptions are a whole-house fan, an evaporative cooler or a fresh-air intake, all of which bring outside air in and should be shut off. If you are not sure which of those your house has, that is worth establishing before the season, not during it.
Is a portable air cleaner better than upgrading my central filtration?
For one room, usually yes, and it is far cheaper. A portable unit sized for a bedroom will clean that bedroom better than a central system cleans the whole house, because it only has one room to do. The honest answer for most families here is both: better central filtration for the general case, and a portable in the room where people sleep.
My house smells of smoke for days afterwards. Is that the ductwork?
Usually not. Smoke odour settles onto soft furnishings, carpet and walls, and it comes off them slowly for days. That is a cleaning problem rather than a duct problem. Duct is worth looking at if the smell is much stronger at the registers than elsewhere in the room, which is a specific and fairly rare pattern — and one we can check.
Do ember-resistant vents reduce my attic ventilation?
A listed vent is designed to provide a stated amount of net free area while resisting ember entry, so it is not simply a blocked vent. What matters is that the replacement is chosen for the area it actually provides, and that intake and exhaust stay in balance afterwards. Swapping vents one-for-one without checking that is how an attic ends up hotter than it was.
Can you assess my whole house for fire safety?
No, and we would not pretend to. We are an HVAC contractor: we can do the vent and ventilation work, seal the ceiling plane where we can reach it, and tell you what we saw in the attic. Roof, siding, windows, decking and clearance around the structure need people who do that for a living, and your local fire agency publishes guidance on all of it.
Get the filtration and the return side looked at before the season.
Both are ordinary spring-service work. In September everybody rings at once.