A series of small signs on transport trucks have a big impact on the way firefighters do their jobs, and without them hazardous materials teams can be put in danger or stopped in their tracks.

The signs are known as dangerous-goods placards, and federal law dictates they be placed on the front, back and sides of a big rig to warn first responders about harmful materials inside.

The 30-centimetre signs can warn about things like explosive materials, poisons and other dangerous goods.

But occasionally a truck's placards are missing or its goods are mislabeled. And that can be a big deal when firefighters are called to the scene of a crash or other emergency.

"The challenge comes when we don't know what we're dealing with and there's potential for hazardous materials that could put our members at risk," said Peter Andrews, a division commander with Halifax Fire and Emergency Services.

Dangerous goods  placards

There are nine dangerous goods placards that cover everything from explosives, radioactive substances and corrosive materials. (Atlantic Provinces Trucking Association)

That was the concern during the recent incident on Halifax's Highway 102, when the driver of a transport truck suffered a medical problem and pulled over. In the back, firefighters found a container full of an unknown substance.

Traffic on one of Halifax's busiest arteries was held up for hours while a haz-mat team tried to determine if the container was dangerous. Ultimately, it wasn't and the substance was identified as a synthetic resin used to repair airplane parts.

'Deliberately and more carefully'

There are a number of reasons why firefighters can be suspicious that trucks haven't been labelled with the proper dangerous-goods placards.

In some cases, firefighters spot potentially hazardous goods that aren't included on the signage. They can also grow concerned when the driver's manifest doesn't match what's on the truck's placard.

Improper signage can cause confusion and a slow down haz-mat teams, but it is necessary to take the extra precautions to make sure no one gets hurt, Andrews said.

"We need to approach more deliberately and more carefully and those things often take much more time because why put ourselves and the public at risk when we can kind of pause and try to track down the information to determine what's on board."

Peter Andrews

Peter Andrews is a division commander with Halifax Fire and Emergency. (Submitted photo)

Dangerous goods are transported each day through Nova Scotia. Everything from propane and paint, to gasoline and oil are on the road.

Under the Transportation and Dangerous Goods Act, every truck driver is responsible for making sure they have the correct dangerous-goods placards on their vehicle.

But four or five times a year, Andrews said his firefighters find themselves in a dangerous situation where they don't know what a truck is carrying.

Transport Truck

If a transport truck is carrying dangerous goods it should have dangerous goods placards visible on its front, sides and back. (The Canadian Press)

The vehicles most often mislabeled are trucks travelling small distances in the municipality or ones carrying a variety of goods, said Andrews. 

Still, truckers have no excuse for not properly displaying their placards, according to Jean-Marc Picard, executive director of the Atlantic Provinces Trucking Association.

He said they are all aware of the signs and should use them any time they're transporting dangerous goods.

"At the end of the day they should verify their information twice and they should do pre-trip inspections before they leave, so there are a few occasions where they can double check as well what they're carrying to make sure the placard is correct," he said.

Jean-Marc Picard

Jean-Marc Picard is the executive director of the Atlantic Provinces Trucking Association. (Submitted photo)

Picard said truck drivers need to manually replace the placards every time they pick up a different load and sometimes mistakes happen — but those instances are rare.

"In terms of major spills or things like that, I mean I can't remember the last time that that has happened," he said. "So we're in good shape as an industry in terms of safety."