United States United States

Environmental Protection Occupational Safety and

Agency Health Administration

EPA 550-F-15-003 June 2015

Chemical Safety Alert:

Safer Technology and Alternatives

Introduction

The Environmental Protection Agency (EPA) and the Occupational Safety and Health 

Administration (OSHA) (EPA/OSHA) issue this Chemical Safety Alert as part of an 

ongoing federal effort to improve chemical risk management, advance safety and 

protect human health and the environment.1 Recent catastrophic chemical facility 

incidents in the United States prompted the President to issue Executive Order (EO) 

13650 - Improving Chemical Facility Safety and Security on August 1, 2013. Feedback 

from industry, workers, community members and environmental organizations 

emphasized the benefits of implementing safer technologies, including those, where 

possible, that are inherently safer, as part of an integrated approach to reducing risks 

associated with hazardous chemicals.

This Alert is one of several actions discussed in the May 2014 Report to the President -

Executive Order 13650 - Actions to Improve Chemical Facility Safety and Security, on 

promoting the use of safer technologies. In the Report to the President, EPA/OSHA

committed to issuing this Alert. EPA/OSHA also committed to developing voluntary 

guidance for facility owners and operators that will offer a more thorough examination of 

alternative measures and safety techniques and how these might be applied to existing 

processes to further reduce chemical and process risks. This Alert is intended to 

introduce safer technology concepts and general approaches and establish the risk 

management framework for the planned guidance document. The guidance will offer 

more practical details and examples. Also, as mentioned in the Report to the President, 

EPA and OSHA will not specify technology, design, or process selection for chemical 

facility owners or operators.

This Alert explains the concepts and principles and gives brief examples of the 

integration of safer technologies into facility risk management activities. Sources of 

information on process hazard analysis and inherently safer approaches to process 

safety are provided.

 1 The statements in this document are intended as guidance only. This document does not substitute for EPA and 

OSHA statutes or regulations, nor is it a regulation itself. It cannot and does not impose legally binding requirements 

on the agencies, states, or the regulated community, and the measures it describes may not apply to a given situation 

based upon the specific circumstances involved. This guidance does not represent final agency action and may 

change in the future.
Chemical Safety Alert – Safer Technology and Alternatives June 2015

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What Does “Safer Technology and Alternatives” Mean?

Safer technology and alternatives means the integration of a variety of risk reduction or 

risk management strategies that work toward making a facility and its chemical 

processes as safe as possible. Usually these strategies are applied to a chemical 

process throughout its life cycle: from initial process and facility design, through initial 

startup, to on-going operations. Development usually starts with a systematic hazard 

identification using process hazards analysis

(PHA) tools like “What If” or “HAZOP” (see 

2008 CCPS). These tools work to identify 

and assess chemical and process hazards.

Follow-on activities develop, refine, and 

implement a hierarchy of hazard controls and 

safeguards (see below) to reduce risks.

The first choice for managing chemical 

hazards and risks is the use of Inherently 

Safer Technology (IST) or Inherently Safer 

Design (ISD). IST and ISD are recognized 

approaches embraced by chemical process 

designers that are most effectively and 

powerfully applied at the process design 

stage. But they are increasingly applied by 

process operators to existing chemical 

processes.

What is the “Hierarchy of Controls”?

The various chemical and process hazards present in a chemical facility are managed 

using a range of controls and safeguards. For example, properly designed and 

maintained vessels, pipes, valves, and temperature and pressure instruments are 

needed to safely store a toxic gas liquefied by pressure. The kinds of controls for 

managing chemical and process hazards range from “inherent” to various layers of 

“add-on” protections. Process safety experts generally prefer using the following 

“Hierarchy of Controls” to manage chemical and process hazards:

1. Inherent: The first preference is to avoid hazards by using non- or lesshazardous substances or materials (e.g., water may be inherently safer than an 

alcohol used as a solvent in a particular process), minimizing the quantity of 

hazardous substances, or simplifying or moderating process conditions to

eliminate or reduce the likelihood or severity of incidents. Although this approach 

is best applied at the process design stage, there may be opportunities as 

described below for existing chemical operations;

2. Passive: Protective hardware or structures added on to a process that provide 

a risk reduction benefit with no action required by personnel and no motive power 

Hazard Identification and 

Process Hazard Analysis (PHA)

 First and foremost, you should

thoroughly know and understand ALL

of the hazards of the chemicals 

present at your site (e.g., toxicity, 

flammability, vapor pressure, 

reactivity).

 Next, you should thoroughly know and 

understand ALL of the hazards 

associated with how you process or 

handle those chemicals (e.g., what 

happens when the power goes off, 

what happens when a tank overfills).

Armed with this information, you can now 

figure out the best ways to manage these 

hazards to prevent chemical incidents!
Chemical Safety Alert – Safer Technology and Alternatives June 2015

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or energy source required (e.g., secondary containment such as dikes and

sumps; blast barriers and shrapnel shields; pressure vessel vent rupture disks; 

tank vent flame arrestors);

3. Active: Safety features or engineering controls added on to a process that 

require active operation of equipment to prevent or mitigate safety hazards (e.g., 

process control devices such as flow control valves and pressure sensors, 

temperature, pressure and flow alarms, control interlocks (e.g. a vessel high level 

alarm triggers a flow valve to close), emergency shutdown systems, vent and 

relief valve scrubbers, vapor suppression systems, de-inventory systems that 

require pumps); and

4. Procedural: Administrative systems that mandate maintaining safe process 

conditions, operating procedures defining safe operating modes and the steps to 

be followed to maintain those modes, training, emergency response procedures, 

emergency warning and evacuation procedures.

What are Inherently Safer Approaches?

As noted above, it is preferable to avoid hazards in the first place. “What you don’t have, 

can’t leak.” (Trevor Kletz, University of Loughborough, UK). Here, in order of desirability, 

are four inherently safer approaches designed to avoid or reduce chemical and process 

hazards and brief examples that illustrate how they can be implemented:

Inherently Safer 

Approach

Examples

1. Substitution

Use non- or lesshazardous materials,

chemistry, and

processes. This 

approach can 

potentially eliminate 

the underlying 

hazard.

Replace a hazardous material with a less hazardous one:

 Replace gaseous chlorine with hypochlorite

 Replace anhydrous gases stored under pressure (e.g., hydrogen fluoride and 

hydrogen chloride) with acid solutions (e.g., hydrofluoric acid and hydrochloric 

acid) that have a lower vapor pressure

 Replace a flammable solvent with a water-based system

Processes that reduce or eliminate a hazard:

 Eliminate bulk oleum and sulfur trioxide storage by using sulfur burning 

equipment onsite

 Convert anhydrous ammonia refrigeration system to a system that uses a 

less toxic refrigerant (e.g., glycol and ammonia) or an ammonia solution

2. Minimization

Use smaller

quantities of

hazardous materials;

reduce the size of 

equipment operating

under hazardous 

conditions such as

high temperature or

pressure.

Reduce hazardous material inventory in process:

 Use pipe or loop reactors vs. batch vessels

 Use continuously stirred, flow-through systems vs. batch reactor vessels

 Adjust reactant ingredient quantities to minimize runaway reaction magnitude.

Reduce quantity of hazardous substances stored as feed or product 

inventory:

 Implement “produce to consume” processes (e.g., eliminate storage of 

chlorine gas by generating chlorine and consuming it as it is produced)

 Generate feedstock on-site at the consumer location

 Implement “just-in-time” deliveries of feed or product (e.g., use of 100-150 

pound cylinders instead of 1-ton containers to supply a process)
Chemical Safety Alert – Safer Technology and Alternatives June 2015

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3. Moderation

Reduce hazards by

dilution, refrigeration,

or process

alternatives that

operate at lesshazardous 

conditions.

Operation at conditions that reduce the potential for and magnitude of 

vapor release in the event a leak occurs:

 Reduce temperature or pressure at which a process operates

 Use a semi-batch reactor rather than a batch reactor to reduce peak 

temperature/pressure in a runaway reaction scenario

 Store gas as a refrigerated liquid in a low pressure vessel instead of at 

ambient temperature in a pressure vessel

4. Simplification

Eliminate 

unnecessary

process or 

chemistry 

complexity to reduce 

the likelihood of 

controls and 

safeguards failing to 

operate properly on

demand.

 Standardize equipment and/or control systems to simplify operator training 

and operations to reduce the potential for human errors

 Reduce the number of process vessels or other components handling 

hazardous materials

 Reduce the number of interconnections to reactors to minimize inadvertent 

flow paths

 Use fully welded construction to eliminate/minimize the potential for flange 

leaks

 Locate pipelines to minimize collision impact

 Minimize the length of hazardous material piping runs; eliminate “dead legs”

 Eliminate situations where rapid operator intervention is required to prevent 

accidents or spills

What Should You Do First?

1. Know Your Chemicals

Your first step should be to thoroughly know and understand ALL of the 

physical and chemical properties of the substances present on your site. Is the 

chemical volatile? Is it toxic? Will it generate a dense gas cloud if it gets 

released? What happens if it is accidentally mixed with water or something 

else handled at the site? Is if flammable? What happens if there’s a fire?

2. Know Your Processes

Next, thoroughly know and understand ALL of the hazards of the ways in 

which the substances at your site are handled and/or processed, including 

those that just temporarily sit in a warehouse. What happens if the power goes 

off? What happens if a storage tank overfills? What happens if the temperature 

rises in the reactor? What happens if the compressor generates too much 

pressure? What if there’s a fire? What happens if a forklift punctures the 

container?

There are many tools to help you gather and understand chemical and process hazards 

such as “What If?” and “HAZOP.” These tools help you step through the many ways 

things can go wrong and to understand the potential consequences when something 

does go wrong (see CCPS 2008).

Armed with this information, now you can figure out ways to manage and control these 

hazards and to reduce risks as low as possible.
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What are Some Approaches to Safety / Risk Management?

Here is a flow chart you can use to take steps to find ways to address the chemical and 

process hazards you identified above. Please note: there is no “silver bullet” or “one 

size-fits-all” solution. You may not be able to eliminate all chemical and process

hazards. In some cases, there may not be practical inherently safer alternatives, and in 

other situations, an inherently safer approach will only reduce part of the potential risk 

associated with the use of a hazardous material or process. You may find you need to 

use multiple “layers of protection” (see below) at various points to make your site safer.

At each point in this flow chart, you should examine whether any of the alternative 

opportunities you might choose is achievable, practical and cost effective and that it 

doesn’t inadvertently transfer risks elsewhere that could either be unmanaged or less 

desirable. For example, reducing chemical inventory too low could trigger the need for 

more frequent supplier shipments at odd hours, increasing the potential for a release 

during transfer operations.
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What are “Layers of Protection”?

The hierarchy of controls concept helps classify safeguards by their reliability, with 

inherently safer approaches generally being highly reliable while administrative 

safeguards tend to be less reliable in preventing harm. However, controlling risk almost 

always requires using multiple approaches. The concept of layers of protection 

acknowledges that individual safeguards are not totally reliable or effective, and thus 

multiple safeguards (“layers”) may be needed to minimize the chances of an initial fault 

propagating to a full blown incident with potential for harm. This is often illustrated using 

the “Swiss Cheese” model for incidents (see Figure 2). In this model, each safeguard 

layer has the potential to fail, with highly reliable safeguards (e.g., “inherent” ones) 

having relatively few 

“holes”, and less reliable 

safeguards (e.g., 

“procedural”) having 

more. While no single 

layer can adequately 

control the hazard, 

having a sufficient 

number of adequately 

reliable safeguards can 

greatly reduce the 

chance of all of the 

“holes” lining up so that 

an incident actually 

occurs.

Facilities typically utilize as many layers as necessary to adequately control their 

process hazards, with preference given to more reliable safeguards. Thus an 

atmospheric storage tank containing a highly hazardous chemical might contain the 

minimum amount of material needed for the process to operate reliably (inherent -

minimization), have secondary containment provisions (passive), use multiple level 

alarms and controls to detect and react to potential overfills (active), and utilize 

operating and maintenance procedures to reduce the likelihood of an overfill or leak 

occurring and to ensure that safeguards operate properly when called upon. By 

ensuring that an adequate number of reliable safeguards are in place and functional, 

the facility can confidently manage the risks associated with the storage tank.

What’s Next?

As noted above, this Alert is designed to introduce approaches and concepts 

associated with safer technology and alternatives; future guidance will offer more 

practical details and examples. In the meantime, you can certainly start to learn more 

about process hazards analysis (see 2008 CCPS), the hierarchy of controls and layers 

of protection. The second edition of the Center for Chemical Process Safety (see 2009 

CCPS) guideline document Inherently Safer Chemical Processes - A Life Cycle 
Chemical Safety Alert – Safer Technology and Alternatives June 2015

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Approach (CCPS 2009) is one of the most detailed references, with numerous 

examples and case studies related to inherently safer applications. More recent 

publications continue to contribute new ideas, tools, and examples in the inherently 

safer arena (See Appendix A).

Ultimately, it is up to you to understand your facility’s risks and what you need to do to 

protect your workers, the public, the environment and your capital assets. As described 

in the CCPS “Business Case for Process Safety” (see 

http://www.aiche.org/ccps/about/business-case) diligence by owners and operators to 

adopt good process safety management practices and to do things the right way, every 

day, enjoy the positive benefits of better operations and continuous improvement.

Finally, the various agencies involved in chemical safety and security are working with 

industry to collect, develop and publicize best practices, including approaches for 

consideration of inherently safer alternatives to existing controls and safeguards (see 

https://www.osha.gov/chemicalexecutiveorder/LLIS/index.html).

Appendix A - References

Reference Bibliography

1978 Kletz Trevor Kletz, “What You Don’t Have, Can’t Leak,” Chemistry and 

Industry, (May 6, 1978).

1985 Kletz Trevor Kletz, “Inherently Safer Plants,” Plant Operations Progress, 

(New York: American Institute of Chemical Engineers, 1985).

2008 CCPS Center for Chemical Process Safety, American Institute of Chemical 

Engineers, Guidelines for Hazard Evaluation Procedures, Third 

Edition (New York: John Wiley & Sons, 2008).

2009 CCPS Center For Chemical Process Safety, American Institute of Chemical 

Engineers, Inherently Safer Chemical Processes – A Life Cycle 

Approach, Second Edition (New York: John Wiley & Sons, 2009).

2010 CCPS Center for Chemical Process Safety, The American Institute of 

Chemical Engineers, Final Report: Definition for Inherently Safer 

Technology in Production, Transportation, Storage, and Use, (July 

2010),

http://www.aiche.org/ccps/documents/definition-inherently-safer-technology

OSHA “Transitioning to Safer Chemicals: A Toolkit for Employers and 

Workers,” https://www.osha.gov/dsg/safer_chemicals/index.html

2012 Hendershot Dennis C. Hendershot, “Inherently Safer Design: The Fundamentals, 

Chemical Engineering Progress (January 2012),

http://www.aiche.org/resources/publications/cep/2012/january/inherentlysafer-design-fundamentals