Inherently Safer Design

Key components

The concept of ISD began with chemical safety expert Trevor Kletz. After a chemical explosion killed 28 workers in 1974 in Flixborough, England, Kletz focused on proactive steps that could prevent subsequent disasters.

Forty years later, Kletz’s mission endures with four key principles of ISD, as outlined by the Center for Chemical Process Safety:

1. Substitute – If a less hazardous material is available, it should be considered.
2. Minimize – Reduce the amount of hazardous materials whenever possible.
3. Moderate – Cooler temperatures or lower pressures often can lead to less hazardous conditions.
4. Simplify – By removing unnecessary complexity, processes become more user-friendly and less prone to failure.

As a basic-level example, Amyotte mentioned the shed in his back yard. Instead of storing gasoline for his lawn mower in a 45-gallon drum, he uses a 20-liter red plastic container. The strategy is inherently safer because he has minimized the inventory of hazardous material.

“That’s one of the basic, fundamental concepts of inherent safety,” Amyotte said. “I could have a 45-gallon drum of gasoline in my shed, and have physical barriers around it and develop safe work procedures and use PPE around it all the time. Or, I could just remove that hazard and just set the very small container there that’s inherently safer.”

No cure-all

Beyond the basics of ISD, plenty of obstacles exist.

What if eliminating one risk creates a different risk? What if certain ISD features are not economically feasible? How much, if at all, should ISD be government-regulated as opposed to voluntary?

“It’s a simple concept at its core,” Amyotte said. “It’s more complicated to implement.”

The complications vary. Take, for example, a plant that substitutes one material for another that is less hazardous, Crowl said.

“But maybe you need more of that material,” he said. “And that material all has to be brought in by truck. So, since you’re transporting more material by truck, you’re actually increasing the risk to the people who live around the routes in which those trucks are shipped.”

Meanwhile, the implementation of ISD does not eliminate the need for administrative controls and other safety strategies.

“Awareness is good, but I think people need to be aware of this concept. Workers and people that live around the community, they have to recognize that there are constraints to this,” Crowl said. “There are economic constraints, there are risk-shifting issues, and sometimes it’s not absolutely clear if indeed one option is more inherently safer than the other.”

Looking forward

As ISD continues to garner attention, many experts see progress. “I think we’re seeing a lot [of progress] in plants,” Hendershot said. “I think the biggest barrier probably is awareness and understanding of the potential, and I think another barrier is just a willingness to challenge the way things are.”

Often, people have approached Hendershot with different versions of the same question. The topic of inherent safety is interesting, they say – but how do you implement ISD?

“I think that establishing a goal is a large part of the solution,” Hendershot said. “Because what you really are talking about is being creative.”

The result of that creativity, combined with advances in technology and a greater awareness of ISD, could help to reduce the frequency of chemical fires, explosions and leaks. It is a continuing journey, Amyotte said, as more people look first to substitute, minimize, moderate, and simplify before turning to safety devices and other strategies.

“It will be very interesting to see where it goes, where we will be in the next five years,” Amyotte said. “Will the U.S. Chemical Safety Board still be writing investigation reports that keep saying, ‘Look, these inherent safety principles were not followed. Had they been, the incident might have been prevented’? Or will we get to the point where it’s being adopted more?”