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With more than a decade of designing authority control and gas detection systems, it still astonishes me that we don’t have a national combustible gas leak detection code. Refrigerant detection, yes. Carbon monoxide (CO) detection, yes. Nitrogen dioxide and CO in enclosed parking structures, yes. We even have hydrogen detection codes for battery storage or battery charging rooms.
These codes all make sense as they add protection and life safety to our designs. But we still don’t have a national requirement to protect mechanical rooms, the facilities they serve or the people working in and around them from the dangers of combustible gas leaks.
Boiler or mechanical rooms are areas where we see the majority of a building’s gas use. Heaters, boilers and burners are all combusting gas. The location of the boiler or mechanical room should be taken into consideration as well; they are typically found in the lower levels or basements of buildings. An explosion event there could damage not only the room itself but the structure of the building, placing all the occupants in danger.
According to the National Fire Protection Association’s “Natural Gas and Propane Fires, Explosions and Leaks Estimates and Incident Descriptions,” report, in the United States, local fire departments respond to an average of 340 natural gas or liquified petroleum gas (LPG) leaks per day with no ignition (https://bit.ly/3rXYRNs). Although gas leaks are much more common than gas ignitions, they can be precursors to devastating events.
Across the United States, about 286 serious natural gas explosions occur each year, causing more than $50,000 worth of damage, severe injury or loss of life. Between 1998 and 2017, 15 people per year, on average, died in incidents related to gas distribution in the United States.
Some jurisdictions and local states are implementing their own requirements. Maine recently experienced a tragic gas explosion that resulted in the death of a firefighter. As of Jan. 1, 2022, it is now legally required in Maine to have a combustible gas detector in any space where combustion is occurring.
The New York Power Authority and the New York School Construction Authority require gas detection systems to be installed in rooms containing boilers rated by the American Society of Mechanical Engineers (ASME). Other municipalities across the nation have suffered from explosions and enacted new regulations for gas detection as well.
Although there is no national code requiring gas detection in boiler or mechanical rooms, the National Fuel Gas Code (NFPA 54) does include some suggestions on what to do if we discover a gas leak. Appendix D suggests these steps: shut off the gas supply, remove the electrical power to the area to stop possible sources of ignition, communicate the condition to people in the area, help them evacuate, and ventilate the area.
The International Fire Code does set out requirements for gas detection systems, including sensor location and system activation (ICC IFC 208, Section 916). Unfortunately, it does not require combustible gas detection in mechanical rooms.
Carbon Monoxide Concerns
One thing we have seen pushing the use of gas detection systems in boiler rooms is the rise in the requirements for carbon monoxide interlocks. Currently, codes require a CO alarm in any space where combustion occurs. Upon detection of dangerous levels, these units send an alarm to warn of the danger. They also may be connected to building fire alarms to communicate that condition elsewhere.
However, all they do is sound an alarm; the combustion process continues and CO levels keep increasing. By creating an interlock with the carbon monoxide detector and the combustion process, the dangerous levels of CO will not only sound an alarm but also shut down the combustion process — warning of a dangerous condition and stopping it from getting worse.
Carbon monoxide comes from the incomplete combustion of fuels. In a combustion process that is not receiving enough oxygen or where there is a defect in the gas train, incomplete combustion will occur.
Water heaters and boilers do create CO as part of their regular operation; it is exhausted through the flue system to the outside. If flues are installed incorrectly, damaged, blocked or experience backdraft, the flue gases can leak back into the area.
Re-burn is another process that multiplies the amount of CO being produced. It occurs when the combustion process consumes most of the available oxygen in the space and then starts to use the available carbon dioxide. If you have a CO problem and do not shut down the combustion process, it is only going to build up and get worse.
Carbon monoxide is a dangerous gas. It attacks the hemoglobin in the blood and inhibits its ability to transport oxygen to the vital organs: the nervous system, the brain, the heart and the lungs. CO is invisible to the naked eye; we can’t smell it and we can’t even tell we are breathing it in.
Left unchecked, carbon monoxide leaks can be fatal. The Centers for Disease Control and Prevention estimates that 10,000 Americans each year are poisoned by CO and need medical treatment; more than 438 people in the United States die annually from CO poisoning.
Because carbon monoxide interacts with a body’s oxygen supply, different levels affect people differently. It is equally dangerous at small levels over a long period and at high levels over short periods. This is why authorities and administrations quote alarm levels as a time-weighted average (TWA).
The Occupational Safety and Health Administration recommends maximum CO levels in the workplace at 50 parts/million (ppm) TWA over an eight-hour window, with a 200-ppm ceiling. The National Institute for Occupational Safety and Health recommends 35 ppm as an eight-hour TWA. The 35-ppm level is where many fire departments require firefighters to wear breathing apparatus before entering buildings.
Interlocking Can Save Lives
The states of Texas, Florida and Georgia all require a boiler room’s CO monitor to be interlocked with the combustion process. This interlock can be via the fuel or power supply to the combustion process or by interrupting the appliances’ external limit contact to disable the combustion process. The states have different criteria for which type of installations fall under these requirements, but all are targeted at the larger heaters — ones above the ASME 200,000 BTU threshold.
An important provision is for the monitors to require a manual reset to reactivate the combustion process after an alarm condition.
These interlocks make sense. For example, when water leak detection systems detect leaking water, they sound an alarm, then isolate the water supply, stopping the condition from getting worse. Using the same premise to stop the creation of more carbon monoxide protects buildings and saves lives.
Installing water leak detection systems is not required by code but is considered a best practice; we should look at combustible gas detection and CO interlocks the same way. These interlocks are being driven by state inspectors and these conversations are increasing. Other states are investigating the feasibility of such requirements, and they will likely become part of the national code soon.
These requirements are intended for the larger ASME boiler installations; however, the industry is moving toward the smaller, more efficient 199,000 BTU/hr tankless units. The problem here is that by multiplying the number of units to get back to the required BTU output of the larger, single boiler, we are multiplying the number of flue and gas connections — and multiplying all the reasons why we would want some protection in that space.
Usually, the argument against adding gas detection to a boiler room is the cost; it’s not code-required, so the owner doesn’t want to pay for it. You don’t want to go to the trouble of specifying something that is going to end up on the value-engineering chopping block.
To combat this challenge, American Gas Safety (AGS) developed the Mini Merlin, condensing a typical gas detection system into a single, easy-to-install monitor. It provides adaptable outputs to isolate fuel and power supplies, interrupts external contacts and communicates with fire alarm control panels. The AGS Mini Merlin provides protection from CO and either methane gas or LPG. Along with audible alarms, the unit provides a clear, digital color display and a convenient reset switch.
Designed for boiler room applications, no programming or setup is required, which is greatly appreciated by the installer. Relays and outputs are already configured to switch at the predefined alarm levels. All gas detection systems are required to be tested on a yearly basis, with results recorded locally. The yearly service is a simple bump test carried out by a servicing contractor or added to a fire alarm service agreement.
Christopher May is the national sales director for American Gas Safety and an associate member of the American Society of Plumbing Engineers’ Florida West Coast chapter. He has more than 20 years of experience in the plumbing industry and is an ASPE CEU presenter. American Gas Safety is an electronics manufacturer based out of Tampa, Fla., providing budget-friendly solutions for gas safety. Visit americangassafety.com.