Detecting the presence of fire - an opinion piece from Industrial Design

Detecting the presence of fireThere are a number of different technologies used to detect the presence of fire, which can come in the form of smoke, heat temperature, infra red radiation from flames or early warning signs from gas detection in the petroleum industry where methane can be ignited.

“The cause of false alarms is not in the detectors themselves but in the overall design and understanding of the standards,” says Mike Fikuart, Managing Director of Industrial Design.

“You have to look for different effects of the same cause. Ionisation detectors such as those found in hotels, offices and accommodation areas ionise a gap between two sensors where smoke particles accumulate. If an ionisation detector is used in a clean room, it will be perfect, but in a dusty environment, it will be triggered more often.”

Another technology is optical, where smoke obscuring infra red light going from one sensor to another will trigger an alarm. Fikuart asserts that they are more stable but will not detect as quickly as ionisation detectors. Nevertheless ionisation detectors cannot differentiate between steam and smoke.

“Heat detectors are perfect for smoky and dusty environments and work in two ways: rate of temperature rise and threshold,” he adds. “They may be electronic or fusible links that melt from temperatures as low as 60 degrees Celsius, for example above kitchen cooker hoods or in hotel laundry chutes.”

Fire extinguishing systems need by regulations to use a scheme called ‘double knock’ verification, where two independent alarms are triggered. The extinguishing medium can be water and/or mist, dry powder, carbon dioxide (CO2) or other such inert gas like argonite.

Fikuart concludes: “We use water mist system on gas turbines in Lybia because they will not put personnel within the enclosure at risk of suffocation like CO2 would. Another method is hypoxic extinction, which reduces the amount of oxygen in air below the 15 percent required to support a flame, but still allows people to work for a limited period of time.”