Officers wearing white forensic-style overalls rushed into a Dundee home after a thermometer fell to the floor, causing mercury to spill.
A woman was then taken from the property and given oxygen.
A team from the Scottish Fire and Rescue Service’s environmental protection unit raced to the address on Craighill Court as the drama unfolded.
The woman involved was taken to Ninewells Hospital as a precaution after being exposed to the potentially deadly substance.
Firefighters in white suits were seen entering the property carrying yellow bin liners and appeared to take items away.
Both the environmental protection unit and the fire appliance left the scene after six hours.
A spokeswoman for the Scottish Fire and Rescue Service said: “Firefighters were called to attend after a thermometer was dropped on the floor, causing mercury to spill.
“Science support services carried out work to secure the scene.
“The woman was administered oxygen and taken to Ninewells Hospital as a precaution.”
Firefighters said there was no threat to the public from the spilled substance.
It is understood the woman has now been discharged from hospital following last Friday’s incident.
Mercury is toxic to the central and peripheral nervous systems.
The inhalation of mercury vapour can also produce harmful effects for the digestive and immune systems, lungs and kidneys. It can be fatal.
One onlooker said: “It all looked very dramatic. At first no one really knew what was going on so it is good to know no one appears to have suffered any real lasting damage.
“It is amazing it all stemmed from a simple thermometer breaking.”