This Isn’t Just a Red Can: What Every Responder Should Know About Fire Extinguishers
When I first sat down with Bobby and Mike for this episode, we thought we were just going to have a quick, 20-minute refresher on fire extinguishers. Instead, we opened the door to an 11-page monster outline and ended up recording one of the most unexpectedly important technical conversations we’ve had in a while.
You’d think after 90+ episodes, we’d have covered it all. But the truth is, fire extinguishers are one of those topics where the more you learn, the more you realize how much you didn’t know.
A Brief (and Bizarre) History
Did you know the first recorded fire extinguisher was essentially a barrel full of fluid and gunpowder? Leave it to 18th-century England to invent a bomb disguised as safety equipment. Ambrose Godfrey’s invention in 1723 literally used an explosion to spread extinguishing fluid. That’s right, let’s blow something up to stop a fire. Brilliant.
Fast forward to 1866 and we get soda-acid extinguishers – think vinegar and baking soda science fair experiments, but weaponized. By 1904, chemical foam extinguishers started resembling what we use today. Then came the infamous carbon tet extinguishers (carbon tetrachloride), which were great at putting out fires but also pretty effective at giving you cancer. So, you know, mixed results.
Understanding Fire Classes Isn’t Just for Exams
We took a walk through the fire classes, from A to K, and trust me, there’s a lot more to it than color codes and triangles.
Class A: Everyday Combustibles
These are your run-of-the-mill fires – wood, paper, cloth, and so on. Class A extinguishers are usually water- or foam-based and are marked with a green triangle. Seems simple, but Mike brought up a good point: modern Class A foams are designed to reduce water’s surface tension. Why? Smaller droplets = better penetration = faster cooling. It’s physics that actually matters on the job.
Class B: Flammable Liquids
Now we’re talking gas, diesel, alcohols, anything that’s a liquid and burns. Class B fires get a red square, and they’re a little trickier. The agents here work by stopping the chemical chain reaction, not just by cooling things down. But here’s the kicker: if you knock down the flames and the fuel is still above its auto-ignition temp, it’s lighting right back up once that agent dissipates.
So yeah, you can put out the fire – but if you don’t remove the heat, you’ve only delayed the inevitable.
Class C: Electrical Fires
Blue circle, non-conductive agents. Pretty straightforward, don’t spray water on live wires. Dry chem and halon-based extinguishers are the go-to here.
Class D: Metal Fires
Here’s where it gets dicey. Yellow star, specialized powders only. If you don’t have the right agent on hand, just protect exposures and let it burn. Using the wrong extinguisher can actually fuel the fire – water on magnesium, for instance, is like throwing a match in a fireworks factory.
Class K: Kitchen Fats and Oils
Black hexagon: the new kid on the block. Mostly seen in commercial kitchens. These are high-temp fires fueled by grease and fats. Water mist is the primary agent here, expanding rapidly to displace oxygen and cool the fire. Bobby had a graphic story about sliding through burning human fat at a crematorium. It’s… exactly as horrifying as it sounds. But hey, the lesson stuck.
Foam Isn’t Just Foam Anymore
We dug deep into foam types – because this is where mistakes happen fast and dangerously. In most departments, foam is foam. You throw it on a Class B fire and move on. But Mike was quick to point out that not all foams play nice with all fuels.
There are:
- Synthetic foams like AFFF (Aqueous Film Forming Foam): fast knockdown, but toxic and not great for long-term vapor suppression.
- Alcohol-resistant foams (AR-AFFF): required when you’re dealing with polar solvents like ethanol. The wrong foam breaks down instantly – there are YouTube videos showing just how bad that gets.
- Protein foams: old-school, biodegradable, and made from things like fish guts (yes, really). Great for post-fire security, but they smell like death and have been phased out in most departments.
If you’re not 100% sure which foam you’re applying, it’s better to ask than assume. The wrong foam doesn’t just fail, it pisses off the fire.
When Dry Chem Is Right, and When It’s Not
Dry chemical extinguishers are kind of the Swiss Army knife of fire suppression. ABC-rated ones cover a lot of ground. But they’re not magic.
Mike explained it well: dry chem interrupts the chain reaction, but it doesn’t cool anything down. So while it may “knock the fire out,” it won’t stop it from reigniting if the surrounding material is still hot. This is especially critical in industrial settings or fuel spill fires.
Also, don’t confuse dry chemical with dry powder – the latter is for Class D only.
Why This Matters for Hazmat
Let’s be honest, for hazmat techs, fire suppression might not be the first thing on your mind. But it needs to be. Fires involving hazardous materials aren’t typical fires. You’re dealing with reactive metals, incompatible chemicals, and extinguishing agents that can trigger chain reactions.
We talked about how using water on a sodium fire is asking for a blast. Or how the wrong foam on an alcohol spill just dissolves on contact. These aren’t academic examples. They happen. And if you don’t know your agents and your fuel types cold, they’ll happen to you.
So What Should You Do With All This?
- Know your symbols: Green triangle (A), Red square (B), Blue circle (C), Yellow star (D), Black hexagon (K).
- Train with your tools. Don’t just walk past the extinguishers on the rig – read them, understand what they’re rated for.
- Stay current: Foam technology is evolving. There are now foams that claim to be multi-class. Know what your department is carrying.
- Push for training that goes beyond the basics. If all you’ve got is “pull, aim, squeeze, sweep,” you’re underprepared.
Closing Thoughts
This wasn’t the episode we expected, but it turned out to be one of the most practical, enlightening ones yet. Fire extinguishers are so common that we often take them for granted. But in hazmat and firefighting, assuming you know how to use one can be dangerous.
If this sparked some questions, or if you’ve got a foam horror story of your own, let’s hear it. Hit us up in the comments, drop us a message, or better yet, share this post with someone who thinks they already know it all.