Free resource · No registration required

The Smoke-Ready Building Plan

When wildfire smoke arrives, the building you are already in becomes your main protection. This plan explains how to prepare it — before the smoke, during the event, and after it clears.

Written for families, medical practices, schools, and community organizations. It recommends no products and no brands, and HBIA sells nothing described here.

Inside a prepared home during a smoke event. The building is doing the work.

Read this part first

This is building guidance, not medical guidance. HBIA does not diagnose, treat, or advise on health status. If you have asthma, heart or lung disease, or any condition that makes you more sensitive to smoke, the decisions about what is safe for you belong to your healthcare provider — ideally discussed before smoke season, not during it.

Everything technical below follows current U.S. EPA guidance, linked at the foot of this page. Nothing here requires an HBIA-certified professional, and nothing here requires you to buy anything from anyone.

What you are building

One room, closed and filtered

EPA calls it a clean room. It is not a sealed chamber or a construction project — it is one ordinary room, closed up, filtered, and kept free of anything that makes particles.

Figure 1. The whole setup: one room closed off, a portable air cleaner running continuously, the HVAC fan circulating through a high-efficiency filter, and the outside air intake shut. Nothing here is specialist equipment.

Part one

Before the smoke — what to settle now

Almost everything that makes a smoke event manageable has to be arranged while the air is still clear. Filters sell out. Advice gets contradictory. Deciding under pressure is the worst version of this.

Filtration gets decided before smoke season, not during it. Know what your system accepts, and keep spares on hand.

Know how you will be told

Set up local emergency alerts, and find your air quality source before you need it. AirNow.gov and your state air quality site both publish current conditions and forecasts. Knowing whether smoke is arriving or clearing changes what you should do.

Choose the room

Pick it now, not later. It should be big enough for everyone in the household and comfortable enough to actually stay in. A bedroom with an attached bathroom works well, because it can be closed off for long stretches without anyone having to leave it.

Sort filtration in advance

Two things to work out while there is time:

• Whether a portable air cleaner sized for that room is within reach, and that it is one that does not produce ozone. The California Air Resources Board publishes a list of devices tested for ozone emissions.
• Whether your HVAC system can take a MERV 13 or higher filter. Not every system can, and forcing one into a system that cannot handle it causes its own problems. An HVAC technician can tell you in one visit.

Have the medical conversation early

EPA advises talking with your healthcare provider ahead of time if anyone in the household has heart or lung disease, and having a written asthma action plan in place if anyone has asthma. Keep at least a five-day supply of food and medication on hand, and know your evacuation routes and how your household will stay in contact.

Part two

During the event — setting up the clean room

Six steps, in the order EPA sets them out. None of them requires special equipment beyond what is described.

Closed, filtered, and comfortable enough to stay in for a long stretch. That is the whole standard.

1

Close the room up

Close all windows and doors — but never in a way that makes it hard to get out. If the room has an exhaust fan or range hood, use it only briefly: running it pulls air from the rest of the house, which can bring more smoke in rather than less.

2

Stay cool without pulling smoke in

Run fans or air conditioning, but close the fresh air intake or set the system to recirculate. Evaporative coolers pull outdoor air by design — if you can safely reach the intakes, cover them with four-inch MERV 13 filters, or use the cooler sparingly. Single-hose portable air conditioners should also be used sparingly in smoky conditions. Heat and smoke together are harder on people than either alone, so do not solve one by ignoring the other.

3

Filter the air in the room

Run a portable air cleaner sized for the room, continuously, on the highest fan setting you can tolerate. If you have central HVAC, a MERV 13 or higher filter with the fan set to "On" rather than "Auto" keeps air moving through it constantly.

Change filters more often than the manufacturer schedule during heavy smoke. If a filter looks heavily soiled when you swap it, that is a signal to shorten the interval further.

4

If a commercial air cleaner is out of reach

A do-it-yourself air cleaner — furnace filters attached to a box fan — can serve as a temporary alternative. EPA's position is specific: use one only when a commercial unit is unavailable or unaffordable, and not as a permanent substitute. Studies indicate a well-built DIY cleaner can perform comparably, but performance depends heavily on how it is assembled, and results vary between units and even between rebuilds of the same unit.

Figure 2. The two things people get wrong: the filter's airflow arrow must point toward the fan, and the edges must seal. A gap lets smoky air bypass the filter entirely, which is worse than it looks — the fan still runs, so it appears to be working.

If you build one, EPA's safety points matter:

• Use a box fan from 2012 or later with a UL or ETL safety marking. Older fans may pose fire risks; if you must use one, never leave it unattended or run it while sleeping.
• No extension cords. No damaged fans. Do not leave children unattended with it running.
• Make sure working smoke detectors are in place throughout the home.
• Keep spare filters, and change them when they look dirty or start releasing smoke odours. During heavy smoke that may be every few weeks, or every few days.

5

Stop adding particles indoors

This is the step people skip, and it is free. While you are sheltering, avoid all six of these.

Figure 3. Six indoor sources worth pausing during a smoke event. Filtration removes particles; these put them back. Vacuuming is the one that surprises people — without a HEPA filter it stirs up more than it collects.

6

Use the room, and air it out when you can

Spend as much time in it as you reasonably can. Avoid exercising in it — heavier breathing means more of whatever is in the air. When outdoor air quality improves, even briefly, open the windows or the fresh air intake and run kitchen and bathroom exhaust fans to flush the room before closing it up again.

Conditions change quickly. A clean room is a tool with limits, and knowing its limits is part of using it well.

When the plan stops working

A clean room is a good tool with real limits. EPA is direct about this: if you cannot stay cool, the power goes out, or too much smoke is still getting in, it may be better to shelter somewhere else. Options include:

• Staying with friends or family outside the affected area
• A public cleaner air shelter
• A large commercial building with air conditioning and good filtration

Conditions change quickly. Stay ready to evacuate regardless of how well the room is working, and follow local authorities over any plan on a website — including this one.

Part three

If someone in the household is already sensitized

This is the part general guidance tends not to cover, and it is the reason HBIA wrote this page rather than simply linking to EPA.

A household that already includes someone with asthma, a chronic respiratory or cardiac condition, or established environmental sensitivity is starting from a different place. The building measures do not change — the planning around them does.

For a sensitized occupant, the difference is not the equipment. It is having decided, in advance, what conditions mean stay and what conditions mean go.

Decide the threshold in advance

Agree with your clinician, ahead of time, what conditions mean shelter and what conditions mean leave. Making that call mid-event, while symptomatic, is the hardest possible moment to make it well.

Write down what happened

Keep a simple log: dates, outdoor air quality, what was running, how long the household stayed in the room. Not a symptom diary — a building record. It gives your clinician something concrete rather than a recollection.

Plan for the power going out

Filtration and cooling both depend on electricity, and outages often accompany fire events. If someone in the household relies on powered medical equipment, that plan has to exist separately and in writing.

Do not stack interventions blindly

Smoke events drive people toward ozone generators, ionizers, and scented "air purifying" products. Some of these add to indoor exposure rather than reducing it. Filtration removes particles; devices that produce ozone are a different category, and EPA's own guidance is to choose a cleaner that does not produce it.

Part four

For medical practices, schools, and community organizations

If you are responsible for a building other people depend on, the same principles apply at a larger scale, and EPA publishes separate guidance for schools and commercial buildings. Four questions are worth answering before smoke season rather than during it:

In a building other people depend on, the decision needs a name attached to it before the day it has to be made.

• What is our highest-filtration option? Know what your HVAC system will accept before you need to order filters, and keep spares on hand.
• Which space is our cleaner air room? Identify it, and know how outdoor air intake is controlled in that zone.
• Who decides, and on what? Name the person who calls it and the air quality threshold they use. An unassigned decision gets made late.
• How do we tell people? Staff, families, and patients need to hear the same thing at the same time, and they need to have heard it once before it matters.

When the air improves, even briefly, flush the room before closing it up again.

Use this, share it, print it

There is nothing to sign up for and nothing to buy. If it is useful to your practice, your school, or your neighbours, pass it on.

Get the free checklist Ask HBIA a question

Sources

The technical guidance on this page follows current U.S. Environmental Protection Agency resources, last updated 18 August 2026. Read them directly:

• EPA — Create a Clean Room to Protect Indoor Air Quality During a Wildfire (also published in Spanish, Chinese, Korean, Vietnamese, Tagalog, Russian and Arabic)
• EPA — Wildfires and Indoor Air Quality in Schools and Commercial Buildings
• AirNow — current air quality conditions and forecasts
• California Air Resources Board — air cleaning devices tested for ozone emissions

About the images on this page. Photographs are composed illustrations created to depict typical conditions. They are not photographs of HBIA clients, projects, or facilities. Diagrams are HBIA's own illustrations and depict no specific product.

No commercial interest in this page. HBIA recommends no products, brands, retailers, or contractors here, receives no referral fees, and earns nothing from any action described. Where a category of equipment is mentioned, the criteria come from EPA, not from HBIA.

Ownership disclosure. The Healthy Building Institute of America was incorporated in Ohio in 2005 and is currently a division of WeSpiritus, LLC. HBIA shares common ownership with Amoldbuster and Apollo Environmental Solutions, which provide environmental assessment and remediation services. HBIA is working toward establishing the institute as a separate legal entity.

Educational content only. This page is educational and does not constitute medical advice, diagnosis, or treatment. HBIA does not diagnose, treat, or interpret health status. Always seek the advice of your physician or other qualified healthcare provider regarding a medical condition, and follow the instructions of local authorities during any emergency.