Here a welder had the heat and the oxygen. Unbeknownst to him, he had the fuel, too.

The ensuing explosion blew this deck right off the boat.

This is what happened. A shop was hired to modify a boat to accommodate

a different outboard engine. The boat was stored outside, where the temperatures

had been below freezing. A foreman brought the boat inside this heated

shop. The boat’s trailer jack was damaged, making

it difficult to elevate the trailer reach, so he positioned the boat with the bow low.

The foreman did a smell test around the boat for gasoline.

He didn’t detect any odour, but never opened the access hatches to check underneath the

deck. He filled in the original bolt holes for the

engine and then used a grinder to prepare the boat’s transom for welding.

Later, a piece of aluminum was welded on to increase the height of the transom.

Overnight, the boat warmed up. Gasoline inside the boat’s full tank expanded.

With the bow low, gasoline flowed from the tank up the filler line.

It then likely seeped out a loose connection at the filler intake, soaking the flotation

foam below that area. Vapours began to fill underneath the deck.

The next morning, a welder began to weld a bung to the transom.

The vapours ignited. Fire flashed back along a vapour trail to the fuel source.

The boat exploded, hurling the welder across the room and parts of the boat up to the 25-foot

ceiling. The welder was injured, but luckily survived.

The danger of flammable vapours is not always obvious, but becomes very real when you’re

doing what is known as hot work. Hot work is work that can initiate fires or

explosions. It includes tasks like welding, grinding,

and cutting. If you can, avoid hot work and use alternatives.

For example, use bolts instead of welding. If you must go ahead with hot work, there

are some key steps you need to take: Identify potential hazards by doing a risk

assessment. This is crucial.

Many hot work accidents occur simply because workers don’t know flammable vapours are

present. Control the hazards.

Here, that would have included repairing the leak, cleaning up any spilled gasoline, venting

the compartment, and then testing prior to and at intervals during the hot work to ensure

the level of flammable vapours was safe. Make sure workers have the safe work procedures,

the training and supervision necessary for doing hot work around flammable or explosive

vapours. Before welding or performing other hot work,

check thoroughly for flammable vapours. Don’t let a hidden danger become a deadly one.