Monitor Carbon Monoxide*
FEATURES
EQUIPMENT
Dependable carbon monoxide indicators are a necessary part of on-sight SCBA cylinder charging systems.
• Information provided by Ketchum Public Relations. Pittsburgh, PA.
The deadly gas carbon monoxide (CO) can disable a firefighter within seconds after invading his air supply. Because CO deprives his brain of oxygen, it may even kill him.
That’s why it is so important for an air cylinder filling system at the fire scene to be equipped with a reliable CO monitor. CO is everywhere at a fire and can easily contaminate a self-contained breathing apparatus (SCBA) during cylinder charging at or near the incident scene.
It spews out of fire engines, pumpers, police cars, supply vans, and other vehicles parked and idling in the area. It emanates from the fire itself as materials smolder and burn. It can also come from the interior of the air compressor if a malfunction occurs.
The Occupational Safety and Health Administration (OSHA) recognizes the danger associated with this deadly gas. They require CO monitors as standard equipment on all mobile air compressor units made or used in this country. The manufacturer of the mobile air charging (MAC) systems has been complying with this stipulation for the past year by installing CO air line monitors in all its units.
Background
The mobile charging system is a European invention that became effective on the fire scene immediately after World War II. Major fire incidents are seldom overcome within the time period and air supply provided by a 30-minute SCBA and one back-up cylinder. For this reason, Europeans developed these mobile cylinder charging systems.
These portable units supplied a continuous feed of fresh air to the firefighter on the scene, enabling him to do his job without risking his life. These early systems contained cylinders of air only for transfer charging, referred to as “cascading.”
Photo courtesy of Ketchum Public relations
The deadly effects of modern urban and industrial blazes are no different than those encountered during World War II. American firefighters are becoming increasingly aware of the toxic respiratory hazards they face, even in routine house fires where burning plastics and synthetic building materials can create carcinogenic fumes. Because today’s firefighter depends so much on SCBA, mobile compressor systems are playing an expanded role in the United States.
A case in point is the fire that took place several years ago at the MGM Grand Hotel in Las Vegas, NV. The use of a MAC system enabled SCBA-clad firefighters to make repeated forays into the burning building to rescue guests. The outcome of the day-long blaze would have been far worse had the compressors not been in use.
MAC systems
There are three basic types of MAC systems, and the CO air line monitor system is standard equipment on all three. There is a trailer version of the MAC system, which is towed to a fire, and two different types of truck versions.
Each model contains an array of different devices. But common components include an air purification system and CO monitor, and a gas or electrical-powered fourstage air compressor capable of delivering pressures to 5,000 psig. This makes it suitable for charging the newer high-pressure (4,500psig) air cylinders, as well as the low pressure (2,216-psig) 30-minute rated cylinders.
The air purification system can eliminate smoke and harmful gases to less than 5 parts per million (ppm). In addition, the MAC systems come with automatic safety” shutdowns that turn off the unit if large amounts of dangerous gases, such as CO, begin invading the system. They are also equipped with cylinder storage racks and a breathing apparatus cylinder charging station with safety shield.
To recharge an air cylinder, a user would fill the charging tank with water and place the air cylinder in up to its neck. The charging tank is made of 1/4-inch hot-dipped galvanized steel, as are its fragmentation deflectors. The cylinder is connected to a stainless steel charging valve, and an adjustable regulator automatically charges the cylinders to the preselected pressure. Charging is controlled by stainless steel soft-seated shut off valves.
Photo courtesy ot Ketchum Public Relations
Filling takes only a few minutes, depending on the cylinder. Safety relief valves prevent carelessness or malfunction to overcharging. On a typical MAC unit, four cylinders can be charged simultaneously, although this capability can be increased or decreased, depending on user specifications.
These MAC system generators can also supply power for floodlights, smoke ejectors, different types of generators and air compressors, radios, even water pumps, and the hydraulic rescue tools.
When a MAC unit is not being used at an emergency scene, it can be used as a stationary air compressor, with power supplied by its 220to 440-volt electric motor.
CO monitors
The CO monitor was designed by a California engineer to be used with the MAC system. The heart of the monitor is its totally sealed long-life electrochemical sensor. Gas enters the sensor by diffusion. The cell oxidizes CO, which provides an electrical signal that is amplified and displayed on an analog meter.
The monitor is usually installed below (downstream) the MAC air compressor and air purification system. It is the last instrument the compressed air passes through before entering the air cylinder.
This placement is vital because CO can contaminate a MAC system from two basic sources: at the air inlet or from within the air compressor.
Air inlet contamination involves CO seeping in from outside air while a cylinder is being filled. This can occur because of the presence of CO at fire scenes. Compressor contamination can occur if the compressor starts to overheat and burn the lubricating oil.
Photo courtesy of Ketcbum Public Relations
The alarms on the unit consist of a bright red light on the front of the monitor and a horn on the bottom that emits a shrill noise. The alarms will sound and the monitor will activate a compressor shutdown if CO concentration exceeds the level preset by the manufacturer. Users can reset it as well.
Most monitors are set to alarm at 20 ppm, a standard level established by the National Fire Protection Association (NFPA). It is also the standard set by both the U.S. Navy and the Compressed Gas Association. The American Council of Government Industrial Hygienists considers 50 ppm to be the minimum amount of potentially harmful exposure.
Summary
The MAC unit that is equipped with a CO monitor serves as an additional layer of protection for the firefighter. It is another tool that makes his job easier and safer.