A tanker truck spewing liquid oxygen from a jammed valve forced firefighters to evacuate the Royal Canadian Mint and close down Sussex Drive for several hours yesterday.

Firefighters were called to deal with the leak around 11:40 a.m.

The truck was unloading liquid oxygen in a driveway south of the mint when the valve got stuck open.

While there was no threat of poison from the fumes from the liquid oxygen, which the mint uses in the silver refining process, Ottawa district fire chief Michael MacCormac said they were concerned about the risk of explosion.

“We don’t want to do anything to the vehicle to create any hazards,” he said.

MacCormac said there was concern that the leak could freeze the tires, causing them to explode and throw metal shards off the rims.

The fire department evacuated the mint and the former war museum next door.

People in sections of the National Gallery of Canada were advised to turn off their air conditioning units and stay away from their windows.

The truck was carrying up to 25,000 litres of liquid oxygen, said McCormac. The delivery to the mint was the first of the day.

The company did a slow bleed of the tanker until it was emptied of liquid oxygen.