Wildfire smoke used to be a regional story. A fire burned somewhere upwind, the sky turned orange for a few days, and building operators waited it out. That pattern no longer holds. Smoke events now last longer, travel farther, and reach cities that never used to plan for them. For building operators, air quality has shifted from a weather concern to an operations problem.
ASHRAE responded in November 2024 with Guideline 44, Protecting Building Occupants from Smoke During Wildfire and Prescribed Burn Events. It is the first industry-wide framework covering commercial, institutional, and multiunit residential buildings, and it puts real weight behind a strategy building automation professionals already know: pressurization.
Why Pressurization Matters
Smoke does not need an open window to get inside a building. It finds loading docks, door gaps, elevator shafts, and any gap in the envelope. Guideline 44 and its public health companion guidance are direct about the fix: keep the building at positive pressure, or cascading positive pressure, so indoor air pushes out instead of letting outdoor air push in.
The concept is simple. Executing it during an actual smoke event is not. Positive pressure has to be balanced against filtration capacity, fan curves, and the ventilation rates ASHRAE Standard 62.1 still requires. Get that balance wrong and a building starves occupied spaces of fresh air without keeping smoke out.
What a Pressurization Strategy Actually Requires
- Seal the envelope. Guideline 44 recommends buildings establish their baseline air leakage and fix known gaps before smoke season, not during it. Loading docks, doors, and envelope damage left over from past renovations are the usual failure points.
- Filter for PM2.5. MERV 13 or better is the accepted benchmark for capturing fine particulate. Two-stage filtration, a MERV 8 pre-filter ahead of a MERV 13 final filter, extends filter life under heavy smoke loading. Buildings on VRF or all-water systems face a harder problem: zone-level equipment often cannot hold a MERV 13 filter, so filtration has to move to the dedicated outdoor air system instead. Some facilities are now pairing particulate filters with activated carbon stages to catch the VOCs and odor that particulate filtration alone misses.
- Automate the response. A PM2.5 sensor tied into the building automation system can disable economizers and demand control ventilation the moment outdoor air quality drops, shift fans into a pressurization sequence, and log the event for later reporting. A manual procedure cannot move that fast, which is why automated overrides, not manual ones, are the direction engineering practice around Guideline 44 is heading.
What This Looks Like In The Field
The building automation supply chain is already building toward this. Pressurization control depends on precise, fast-responding damper positioning across outdoor air, return air, and exhaust, not dampers that only know open and closed, which is the kind of work actuator technology from companies like Belimo is built for. Controller and sensor platforms from iSMA CONTROLLI support the same PM2.5-triggered logic Guideline 44 describes, giving smaller and mid-size buildings a path to automated smoke response without a full BAS overhaul. At the platform level, Johnson Controls has folded smoke and air quality response into its broader building analytics offerings, treating wildfire events as a data problem alongside energy and comfort. None of this reaches a building without a distribution partner getting the right actuator, sensor, or filter rack on site before smoke season starts, which is where supply partners like Cochrane Supply fit in.
Standalone systems are entering the market as well. HB SmokeReady, launched by C5 Plus, packages PM2.5 baselining, readiness modes, and real-time monitoring into one program built on Guideline 44 methodology, aimed at property teams without a controls integrator on staff.
The Forcasting Layer
The newest piece is prediction. Researchers, including a team at the University of Utah, are developing AI-driven smoke forecasting tools designed to model smoke behavior at a far more local scale than regional air quality alerts allow. That matters because exposure varies block by block, not city by city. Two similar buildings a mile apart can register very different PM2.5 levels depending on airflow patterns and exposure angles. As this forecasting data matures, it is expected to feed directly into building automation platforms, giving buildings a head start on pressurization before smoke arrives rather than after sensors detect it.
The Takeaway
Pressurization is not new to building automation. What is new is the expectation that it happens automatically, triggered by real air quality data, coordinated with filtration strategy, and documented for occupants and regulators alike. Guideline 44 gives the industry a shared playbook. The actuators, sensors, and platforms to run it already exist. The buildings that handle the next smoke season best will be the ones that tested the sequence before they needed it.
Sources
Wildfire Smoke Is Becoming a Building Technology Problem, Propmodo
How Commercial Buildings Can Stay Ahead of Wildfire Smoke, Camfil Clean Air
Protecting Indoor Environments from Wildfire Smoke, M-M Insights
Wildfire Smoke HVAC Filtration, Advanced Filtration Concepts
C5 Plus Announces HB SmokeReady, EIN Presswire
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