Intrinsic Safety & Thermal Imaging

Brad Harvey discusses some of the various terminologies and addresses the environmental conditions that set the bar for electrical safety requirements.

“Intrinsically safe” is a term that seems to be proliferating in the fire service. It is being inserted into many different National Fire Protection Association (NFPA) standards and is beginning to show up in literature for many different items sold in the fire service.

Intrinsic safety is a term that is widely used to describe an electrical or electronic device designed in such a way as to render it safe for use in an explosive atmosphere, even under abnormal operating conditions. What’s not to like about that? As firefighters, you routinely enter explosive or potentially explosive atmospheres, right? What’s not to like about a piece of equipment that will not ignite in that atmosphere, even under failure mode?

The fact that intrinsic safety seems so intuitive is the very reason the term and feature are proliferating; however, like many terms developed by electrical engineers, or engineers in general for that matter, the term is much more nuanced than it appears. As with any emerging technology feature, you must understand the nuances of those terms so you can sort out myth from fact and keep from being lulled into a false sense of security.

This month’s column discusses some of the various terminologies and addresses the environmental conditions that set the bar for electrical safety requirements. Next month, we will discuss design modifications for electrical safety and the future of some of the standards. If you or your department have deemed intrinsically safe as a product requirement, it is essential that you understand the nuances of that requirement.

The term’s evolution

“Intrinsically safe” is actually a fairly generic term that does not convey much. Referring to an item as intrinsically safe is like calling a self-contained breathing apparatus (SCBA) a respirator. The Occupational Safety and Health Administration (OSHA) describes respirators in terms of Applied Protection Factors (APF) that range from an N95 filtering facepiece with an APF of 10 all the way to a positive-pressure SCBA with an APF of 10,000. OSHA uses APFs to describe the equipment suitable to protect the wearer from the atmosphere or contaminant to which they are exposed. Intrinsically safe works the same way.

Although different sources cite different points of origin, at least one contributor to the need for standards was coal mines. In the 1920s and 1930s, as coal mining was booming around the world, several unfortunate explosions, determined to be caused by electrical devices in the mines, signaled the need for precautions when introducing spark or other thermal hazards to potentially explosive atmospheres. These atmospheres are defined as “hazardous locations.”

Although the exact chronology of standards development is difficult to determine, the NFPA formed a committee to classify hazardous locations as early as 1955. Today, the National Electric Code (NEC), Canadian Electric Code (CEC), International Electric Code (IEC), European Committee for Electrotechnical Standardization (CENELEC) and others all classify hazardous locations.

The development of these standards was originally intended to address electrical equipment and circuits that were installed or employed in hazardous locations. The origins of the standard never really considered the advent of rechargeable, portable, battery-operated devices and certainly never considered the power that can be generated by advanced battery materials. As the consumer appetite for smaller, longer-lasting and more powerful batteries continues, the risks that the power sources can pose in hazardous locations increases as well.



Like any other emerging feature or technology, intrinsic safety can take on buzz-word status. The problem becomes that the more trendy a buzzword becomes, the more nebulous the meaning. In the case of intrinsic safety, the term is supposed to convey a meaningful aspect of safety. There is no room for nebulous when it comes to safety.

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