The Dumpster Fire From a Battery in the Trash

Why this matters

A lithium-ion tool battery that has been dropped, crushed or punctured can sit quietly for hours and then go into thermal runaway: the cells heat themselves, vent flammable gas and ignite each other one after another. In a dumpster, surrounded by cardboard and packaging, that is a fire with its own fuel supply, and in a packer truck it is a fire inside a vehicle full of paper. Battery fires are now a recognized and growing cause of fires in waste trucks and at waste and recycling facilities, and EPA has published an analysis of them. This case starts with the fire, because nothing else can happen until it is out, and works back to a cracked battery pack thrown away the previous afternoon.

The first fifteen minutes

At 5:35 am on a Thursday the warehouse lead of a 16-person HVAC and electrical shop pulled into the lot and saw smoke curling from under the lid of the shop's 6-yard front-load dumpster. The dumpster sat in a fenced enclosure about 15 feet from the back wall of the building. He did these things, in this order, and each one was right:

He stayed back and upwind, and called 911 from his truck. Smoke from a battery fire carries toxic and corrosive gases, hydrogen fluoride among them, on top of ordinary smoke from burning trash. He did not walk into it to get a better look.

He did not open the lid. Lifting the lid feeds a smoldering fire a rush of air and puts your face at the opening as it flares. A closed steel lid starves the fire and keeps it in the box.

He did not use the extinguisher from the shop wall. A portable extinguisher is for a small fire you can fight from an exit. A dumpster of burning cardboard with a battery at the bottom of it is neither, and a lithium cell can keep burning or reignite after its flame is knocked down. He kept the extinguisher in hand only to protect his way out.

He judged the building. At 15 feet, with the wind away from the wall and nobody yet inside, he did not need to evacuate anyone. If the box had been against the wall, or the wind had been driving smoke into the building, the plan was to keep everyone out and meet arriving staff at the front of the lot.

He moved the two vans parked beside the enclosure, which he could reach without passing downwind of the smoke, and then stayed at the lot entrance to meet the engine and tell them two things: what was in the dumpster as far as he knew, and that batteries were a possibility.

The fire company opened the box with a hose line ready, flooded it, and pulled the top layer out with hooks to reach the seat of the fire. They stayed until the contents stopped steaming, because battery debris can rekindle. That was their job, not the shop's.

Containing what was left

With the fire out, the box was a sodden, half-burned load with an unknown amount of battery debris still in it, and the shop had three ways to handle it. Costs below are in regular pickups, the unit the hauler's agreement used.

Leave it until the next scheduled pickup, two days away. Cheapest on paper. Rejected, because the fire captain warned that damaged cells in the debris could reignite hours or days later, and a second fire in the same box would be against a building that was now occupied.

Have shop staff pick out the battery remains and leave the rest. Rejected outright. Nobody at the shop knew which pieces were live cells, the debris was wet and sharp, and digging through it by hand is how someone ends up holding a cell as it vents.

Call the hauler for an emergency swap and haul that morning. Chosen. The hauler pulled the box, dropped a replacement, and took the damaged one with its contents directly to a facility that agreed to receive it, with the load declared as fire debris that might contain batteries. The emergency service was billed as one extra pickup. The agreement made the shop responsible for container damage beyond normal wear, and the melted plastic lids and a warped side panel were billed at replacement, about four regular pickups. Total: about five regular pickups, against a shop that normally used about nine a month.

Runoff and insurance. The water the fire company used was an emergency discharge, and it was theirs to manage. Once they left, the scorched, residue-coated enclosure pad was the shop's, and it was cleaned by sweeping and absorbent into a container, not by hosing it into the storm drain at the lot edge. See related: Wash Water and the Storm Drain Rule. The office photographed the enclosure, the box and the replacement, saved the fire department's incident number, and notified the shop's property insurer the same morning.

Working back to the cause

The fire investigator, sifting the material his crew had pulled out, showed the warehouse lead the seat of the fire: the front corner of the box, about a foot below the top of the load. In the char at that spot was the melted housing and latch of a cordless tool battery pack, with its cylindrical cells split open. The shop ran one cordless tool platform across every crew, and the latch was theirs.

That pointed at a battery, but the shop checked the other candidates against the record rather than taking the obvious answer:

A cigarette. The shop's smoking area was at the far side of the lot, and no butts were found near the enclosure. A discarded cigarette also tends to start a fire at the surface of a load, early in the evening; this one started a foot down, in the early morning.

Oily rags. Rags that self-heat can ignite hours after they are balled up. But the shop's rags went into a self-closing safety can, emptied daily into the used rag service, and the can's log showed it emptied Wednesday. No rag remains were found at the seat.

Somebody else's trash, or arson. The dumpster had a locking lid, and the lock was found intact and closed. No tampering, no foreign debris.

The battery. The tool crib assigned 22 packs across the crews. A count Thursday morning found 21. The missing one belonged to an electrician, and his job notes from Wednesday held the rest of the story.

What the record showed

At about 2:30 pm Wednesday the electrician's drill had fallen off a stepladder onto a concrete garage floor. The pack's housing cracked at one corner. He swapped in a spare from the van and noted on the job: "dropped drill, battery cracked, replaced from stock." At end of day, about 4:50 pm, he cleaned out the van and dropped the cracked pack into the dumpster with the cardboard. It had not felt warm.

From 4:50 pm Wednesday to 5:35 am Thursday is 12 hours and 45 minutes, about 13 hours. That gap is the most important fact in this case. A dropped cell can carry internal damage, such as a crushed separator between the electrodes, that does nothing visible until it shorts internally and heats. A pack that is cool when it is thrown away proves nothing about whether it will stay cool.

What the electrician did not know was the part that mattered: that a cracked pack is treated as a damaged battery the moment it cracks, whether or not it is hot. What the shop did not have was anywhere to put it. The shop's battery pail was for intact batteries headed to the recycler, and it sat in the parts room, not at the van door. The dumpster was ten steps away. The note on the job ticket was accurate and nobody read it as an alarm.

The fix: a bin, a rule and a trigger

The bin. A steel can with a tight lid, a third full of dry sand, on the concrete pad outside the van door, labeled "DAMAGED BATTERIES ONLY - NOT TRASH." Any battery that is dropped hard, cracked, swollen, punctured, wet, hot or smells sweet or solvent-like goes in it, buried in sand, the same day. The can sits outside so that if a cell does vent, it vents in the open, away from the building and the other waste. Handling, packaging and shipping the contents follows the shop's damaged-battery procedure. See related: The Damaged Lithium Battery Handling SOP.

The rule. No battery of any kind goes in the dumpster. Intact batteries go in the intact battery pail, which moved from the parts room to the waste area by the van door, where unload happens. The dumpster lid now carries a placard with a picture of a tool pack and the words "never in here, see the can by the door." See related: Lithium-Ion Batteries in Tools, Vans and Customer Equipment, The End-of-Day Van Waste Unload SOP.

The trigger. A job note containing "battery" with "dropped," "cracked," "swollen" or "hot" now flags to the office, which confirms with the tech by end of day where the pack went. The electrician's note would have produced that call at 2:30 pm, more than two hours before the pack reached the dumpster.

The count. The tool crib count moved from quarterly to monthly, because the only reason the shop could name the pack's owner the next morning was that someone had counted recently enough to notice one missing.

How they confirmed it held

Over the next three months the damaged-battery can received four packs: two dropped, one swollen from a hot van dashboard, one with a cracked case from a pickup truck bed. Each came with a flagged job note and an office confirmation. None was found in the dumpster on the owner's monthly look under the top layer. Four damaged packs in three months at a 16-person shop is the useful number here: it says the Wednesday pack was not a freak event but an ordinary one, a little over one a month, that the shop had been throwing away for years without a fire.

What would have changed the outcome. Had the dumpster been against the building wall, the same pack would have been a structure fire. Had it been a pickup day, the fire would have started in the packer truck, with the driver, at the transfer station, and the hauler's claim against the shop would have been for a truck, not a lid.

References

• EPA, analysis of lithium-ion battery fires in waste management and recycling (2021)
• NFPA guidance on lithium-ion battery hazards and fire department response
• Your hauler's service agreement, including container damage and emergency service terms
• See related: The Shop Dumpster and What Gets a Hauler Fine, The Damaged Lithium Battery Handling SOP, Setting Up a Segregated Waste Area at the Shop