G-Shield Fire

The Toxic Twins

In the fire service, carbon monoxide and hydrogen cyanide are often called the toxic twins.

Carbon monoxide is the one people know about. Hydrogen cyanide is the one that has changed. It comes from burning synthetic materials, and modern buildings are full of them. Foam furniture, carpet, insulation, wiring, plastics and composites can all release hydrogen cyanide when they burn.

The two gases act on the body in different ways, and exposure to both at once can be more dangerous than either alone. Neither has a useful warning smell, and both can be present during overhaul and in the smoke drifting around an incident, not just inside the fire.

The G-Shield Fire exists so a crew knows what’s outside the vehicle before anyone steps into it.

Reading the Air Before the Door Opens

The sensors mount on the outside of the vehicle, and the display goes in the cabin.

That arrangement is the whole point. A detector worn by a person tells you what you’ve already breathed. A detector on the vehicle tells you what you’re about to walk into, while there’s still a decision to make about breathing apparatus, positioning or approach.

Readings are live and continuous, so the crew sees conditions change as the vehicle moves. On a fire ground where the wind shifts, that’s the difference between reacting and being caught out.

G-Pods: Sensor Changes in Seconds

The sensors are G-Pods: smart, single sensor cartridges with their own data storage. They’re waterproof to IP66 and IP68, arrive pre calibrated, and plug straight into the sensor platform.

That matters operationally. An appliance out of service is an appliance not responding, so a sensor change that takes seconds at the station, rather than a day at a workshop, keeps the vehicle available. There’s no calibration to do when fitting, and no configuration to set, because each G-Pod carries its own identity and calibration data.

The platform is built to take more than the two gases currently offered. An onboard circuit provides a universal interface across different gases and sensor technologies, and the system can be configured for other applications and environments, including refuge chambers.

Built for Outside, Displayed Inside

The sensor platform is 316L stainless steel, rated IP66 and IP68 (1.2 m for 1.5 hours), and fits to the vehicle with an M25 thread.

Each part of the system has its own operating temperature range. The sensor platform runs from -20°C to +70°C. The CO G-Pod runs from -30°C to +50°C, and the HCN G-Pod from -40°C to +40°C. The cabin display runs from 0°C to +40°C. So the working range for a fitted system is set by the sensors installed, not just the platform.

The touchscreen display panel mounts in the cabin at 116 x 77.5 x 20 mm, so it fits a dash aperture without a bracket. An optional VESA 75 compliant enclosure is also available. The display and sensor platform weigh 220 and 230 grams, which is negligible on a fire appliance.

Power runs from 9 to 30 VDC, covering 12 and 24 V vehicle systems, with a separate accessory input on the same range so the unit knows the vehicle’s ignition state. The display typically draws 2 W, and the sensor platform less than 1 W.

Warning and Danger, Not Just Alarm

There are two alarm points rather than one: a warning level and a danger level.

That distinction is worth having on a fire ground. A warning tells the crew the atmosphere is getting worse, and to think about breathing apparatus. A danger alarm tells them the decision has been made for them. A single alarm point forces a choice between nuisance alarms and late alarms.

By default, carbon monoxide alarms at 30 ppm (warning) and 200 ppm (danger), and hydrogen cyanide at 4.7 ppm (warning) and 10 ppm (danger).

An internal sounder alerts occupants and can be acknowledged from the cabin. An optional display enclosure adds integrated audible and visual alarms, and the display can also drive customer supplied external alarms. Alarms can be viewed and acknowledged from different positions on the vehicle, which suits a larger appliance where the crew isn’t all in one place.

On Board Memory and Outputs

The unit logs readings to on board memory. For a fire service, that’s more useful than it first sounds. A crew exposure record, evidence of conditions at an incident, and data for a post incident review are hard to reconstruct afterwards, and easy to download.

Output relays are rated 5 A, so the detector can also drive something on the vehicle rather than only informing the crew.

The G-Shield Fire is designed and built in Australia by Gastech, in an ISO 9001 certified facility.

Where It’s Used

Fire appliances, pumpers and light tankers, rural and bushfire service vehicles, airport rescue and firefighting, mine rescue vehicles, emergency response vehicles on industrial and resource sites, hazmat response units, ambulance and paramedic vehicles attending fire grounds, marine and port firefighting units, and vehicles responding to electric vehicle and battery incidents.