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In Hazmat Size-Up and Initial Actions
January 2026
By Kenny Larson
The definition of what qualifies as a hazardous materials (HazMat) incident has changed dramatically in recent years—and so has the approach to handling it. We can no longer prepare solely for overturned fuel tankers or leaking shipping containers. Today’s HazMat calls are just as likely to involve chemical suicides, lithium-ion battery fires, or alternative fuel vehicles.
Best practices are evolving almost weekly as new information emerges. While “bread and butter” events like natural gas leaks and gasoline spills still occur, HazMat has moved into our neighborhoods, homes, and workplaces. None of this should deter or overwhelm the local responder because you are still the hero at these scenes, and the tools you already have can make a life-saving difference. After all, no one has ever been saved by a rescuer in a plastic HazMat suit.
Beyond “The Thumb Rule”
Most of us were introduced to HazMat awareness through “The Thumb Rule” or “The Donut Hole.” The idea that if you can cover the entire incident with your thumb at arm’s length, you’re far enough away. The instruction was simple: recognize the hazard, call for help, and stay clear.
That’s a sound defensive posture—but it’s not always enough anymore. When hazardous materials make their way into homes, cars, or confined spaces, responders must move past “The Thumb Rule.” We need crews capable of identifying a situation, making a risk-based assessment, and taking calculated actions using the tools already on the rig.
“Dude, Don’t Breathe It”
If there’s one principle that never changes, it’s this: “Dude, don’t breathe it.” It’s not a scare tactic—it’s sound operational advice. A firefighter in full structural gear and SCBA can be a superhero in the initial stages of a HazMat event.
Your SCBA provides protection from most airborne threats long enough to make a safe, targeted rescue. But this isn’t a substitute for training or knowledge—it’s a motivator to learn more. Tools are only as effective as the skills behind them.
The Familiar Logic of Size-Up
At its core, HazMat is still about scene size-up and risk assessment. The questions haven’t changed:
What’s happening?
Who needs help?
What will happen if we act—or don’t act?
What are the risks, and how can we reduce them?
HazMat incidents follow the same decision-making process as house fires, water rescues, or vehicle extrications. That’s why local responders—you—remain the experts in protecting the community. Coordinate with your regional HazMat team, seek refresher or initial training, and talk through “what-if” scenarios with HazMat technicians. You’ll find that many solutions rely on proper size-up, risk-based decisions, and the tools you already know how to use.
The 3/30 Rule: A Practical Rescue Guideline
The 3/30 Rule is one such tool—a guideline to help emergency responders balance life-saving efforts with safety during HazMat rescues. It defines how long a responder can operate in a contaminated area while wearing structural PPE and SCBA:
3-Minute Rule: When rescuing unconscious or seizing victims, structural PPE with SCBA provides about three minutes of effective protection. These victims are typically within line of sight or a known area.
30-Minute Rule: When rescuing conscious and mobile victims, the same equipment can provide up to thirty minutes of protection, allowing for controlled rescue and evacuation efforts.
This rule does not apply to confined or below-grade spaces, where vapor concentrations can be significantly higher and protection time is drastically reduced. Some situations—such as those involving fluorine-containing gases or explosive atmospheres—should not be approached until the environment can be changed or mitigated.
The 3/30 Rule isn’t a license to take unnecessary risks—it’s a framework to help you understand what’s possible with the equipment and knowledge you already have.
Tools You Already Own
If there’s one theme to take away, it’s that you already have what you need. Structural PPE, SCBA, and basic ventilation tools—like a fan to push a vapor cloud away or replace contaminated air—can all make a measurable difference.
And don’t overlook one of the most powerful tools in your pocket: the cell phone. Quick communication with your regional HazMat experts can provide critical confirmation and reassurance. Their advice will likely sound familiar: “Dude, don’t breathe it,” and “Remember the 3/30 Rule.”
With those two principles—and the knowledge you already bring to every call—you can move confidently beyond “The Thumb Rule” and make a real impact in your community’s next HazMat emergency.
About the Author
Kenny Larson has served in the Iowa Fire Service for more than 23 years, working in both full-time and combination departments. He currently serves as a District Fire Chief with the Des Moines Fire Department, overseeing operations on the city’s East Side as part of the 1st Division. Chief Larson is dedicated to advancing practical, safety-driven approaches to HazMat and fireground operations, focusing on empowering firefighters to make confident, informed decisions in dynamic environments.
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