Off-Site Consequence Analysis

EPCRA and Fires

EPCRA is not designed to handle every sort of disaster involving chemicals. One thing that EPCRA and its emergency planning procedures do NOT address is what happens at a facility when there is a fire involving the chemicals on-site. The extreme heat of a fire, the extraordinary amount of chemicals that could mix, be degraded from other chemicals, or be created during a fire, makes it almost impossible to determine what toxics would be in the smoke of such a fire. Also, the normal computer software programs used by emergency planners is not suited for fires involving chemicals. EPCRA is more focused on the spill of chemicals and the hazards and effects of such a chemical spill.


There are emergency planning computer programs that "model" just how far a cloud or plume of chemicals from a spill would travel do not include "modeling" for fires. CAMEO and ALOHA are the names of two commonly used software programs for computer modeling. This plume or cloud modeling is called an "off-site consequence analysis." The computer "modeling" programs do have other limitations, and not all types of chemical spills and how far the chemicals would travel is known or easily obtainable. In order for the modeling software to work, there must be sufficient studies of the different chemicals to know how they might disperse into the air, and in many cases, the data is incomplete.

An example of this is Anhydrous (waterless) Hydrofluoric Acid and Aqueous (with water) Hydrofluoric Acid. Because there have been many tests on Anhydrous Hydrofluoric Acid, which is a very deadly and poisonous chemical, the modeling software is able to make predictions about the plume from a release of this chemical. But Aqueous Hydrofluoric Acid, which is just as deadly if ingested, contacted, or inhaled, is not yet studied or understood enough to be able to "model" a plume from a release or spill.

To work out the modeling for a chemical spill, there are many factors to be considered. The information about the weather conditions (which can change many times during a chemical spill), humidity, wind direction and wind speed, and other factors can be involved. The cloud of chemicals may be invisible, or white, or colored. It may be circular, or long and thin. The cloud or plume could move along the ground and accumulate in low-lying areas if it is heavier than air, or move quickly into the sky away from the ground if it is lighter than air. See Off-Site Consequence Analysis.

Also, the total amount of the chemical involved, the properties of the chemical, the type of container or tank the chemical is in, the size of the hole that the chemical is spilling from, how fast the chemical is spilling, whether the chemical is under pressure, all of these are factors in determining how far away from a spill that there may be a hazard.

Of course, computer "models" are only an educated guess based on a variety of assumptions, and sometimes the "models" don't work out as expected. For example, when Anhydrous (waterless) Hydrofluoric Acid was tested in Nevada in the 1980's under a variety of release scenarios, none of predictions were correct. The scientists had predicted that the majority of the Anhydrous Hydrofluoric Acid, pressurized and heated, would fall into a catch basin after being released from just three feet off of the ground. But none of the Anhydrous Hydrofluoric Acid reached the ground. Instead, it all vaporized. Many chemicals, but by no means all of them, have been studied under various release scenarios to determine how far they would likely travel from the place they are spilled. There is no requirement that this information be known before a chemical or chemical mixture can be used in industrial processes. There is still no certain way to model the off-site consequences of a spill of Aqueous (with water) Hydrofluoric Acid, for example. Certainly, after the water evaporates from the Aqueous Hydrofluoric Acid solution, which is a function of temperature, weather conditions, relative humidity, time, etc., the spill would begin to behave like Anydrous Hydrofluoric Acid. These off-site consequences are a function of wind speed, temperature, relative humidity, weather conditions, topographical differences (i.e. hills, valleys, tall buildings), etc. This is another reason why communities will want to know that the "off-site consequence analyses" have been conducted for the various chemicals are stored near or in their midst. When the accidental spill happens, it is too late to start determining this information. Preparation means preparing in advance!

The distance from a chemical spill or release that evacuations and shelter-in-place may be instituted depends on what information is known about the chemical, but this information may change as new studies and information about the chemical are available. Often, the OSHA PEL (Occupational Safety Health Adminstration Permissible Exposure Limit) value for a chemical is the basis for determining what is the "safe" exposure limit for the public around a spill. The common emergency response practice is to allow exposure to a "safe" level of a chemical at 100 to 1,000 times less than the OSHA PEL.

But these OSHA PELs have been known to be wrong before. For example, Methylene Chloride once had an OSHA PEL of 500 parts per million (ppm), and now, over a period of ten years, that PEL has been revised downward to 25 ppm. 1,3 Butadiene once had an OSHA PEL of 1,000 ppm, and this has now been reduced to 1ppm. Of course, earlier emergency planning and response scenarios (models) would have been based on numbers that were too high. The "safe" zone for evacuating and protecting people would have been incorrect. This is another reason why avoiding exposure to any chemical from a release or chemical spill is a good idea.

It is not good practice to make the OSHA PEL the "acceptable" level of exposure to the public in the event of a chemical spill or release. Under OSHA, employers have a duty to protect the workers and must pay for medical treatment and attention if chemicals at the worksite injure employees. Generally, if a non-employee has been harmed by chemicals from a spill at a facility, there is not any automatic avenue for medical treatment and attention for the non-employee, hence EPCRA's requirements for that specific medical information at the time of the emergency and afterwards.


OSHA PELs are based on the concept that the worker is exposed to chemicals for no more then 8 hours at a time. The worker has "downtime," or time away from the chemicals and workplace, allowing the body time to remove or lower the amount of chemicals in the system. Continuous exposure with no downtime does not allow for the body to cleanse itself, therefore continuous exposure limits can cause the body to accumulate the chemical at a greater rate than it can expell it, a potentially dangerous situation. OSHA PELs do not apply to continuous 24-hour per day exposure.

Firefighters responding to a chemical spill or release should determine the OSHA PEL for the chemical spilled and consider the "safe" zone for the public to be at 1/100th or 1/1,000th the OSHA PEL. There may be quite a problem in determining exactly what chemical has been spilled, so this task for firefighters is not easy.

The firefighters responding to a chemical spill or release often consider or use another standard, the IDLH, or Immediately Dangerous to Life or Health. The IDLH actually is a 30-minute "safe" exposure limit; the words "immediately dangerous" have a different connotation. What the IDLH level is also helps emergency responders determine whether to use a respirator, or what type of respirator to use, in a response. Obviously, knowing what these different IDLH standards are, what they mean, and how to interpret them is something to be done long before any accident occurs. This is another reason why chemical emergency preparedness depends on real-time, valid facility chemical inventory information. Proper emergency training and equipment are needed to prepare firefighters to deal with the particular chemical hazards that are actually present in the community.


To further complicate matters, the OSHA PEL may not be an entirely correct figure. The National Institute of Occupational Safety and Health (NIOSH) has created standards for exposure to chemicals with Recommended Exposure Limits (REL) that are usually below OSHA PEL standards. And the American Conference of Governmental Industrial Hygienists (ACGIH) has created standards named Threshold Limit Values (TLVs) and Biological Exposure Indices (BEIs) that are also generally below OSHA PEL levels.

NIOSH Recommended Exposure Limits (REL) are developed under the authority of the Occupational Safety and Health Act of 1970 (29 USC Chapter 15) and the Federal Mine Safety and Health Act of 1977 (30 USC Chapter 22). NIOSH develops and periodically revises recommended exposure limits( RELs) for hazardous substances or conditions in the workplace. NIOSH also recommends appropriate preventive measures to reduce or eliminate the adverse health and safety effects of these hazards. To formulate these recommendations, NIOSH evaluates all known and available medical, biological, engineering, chemical, trade, and other information relevant to the hazard. These recommendations are then published and transmitted to OSHA and Mine Safety and Health Administration (MSHA) for use in promulgating (creating) legal standards. The operative word here is "recommend." NIOSH is purely an advisory body and has no legal authority of its own. OSHA is the only agency who has the legal authority to set exposure standards. The main difference between OSHA and NIOSH is that OSHA uses an 8 hour time weighted average while NIOSH uses a 10 hour time weighted exposure limit.
Time-weighted average means averaged over a period of time, so higher and lower exposure levels can occur.

Also, NIOSH sets "ceilings" for which exposure levels cannot be exceeded at any time. OSHA rarely sets "ceiling" exposure levels. OSHA is not always successful in implementing NIOSH's recommendations: In July 1992, the 11th Circuit Court of Appeal in its decision in AFL-CIO v. OSHA, 965 F.2d 962 (11th Cir., 1992) vacated more protective PELs set by OSHA in 1989 for 212 substances, moving them back to PELs established in 1971.

American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Values (TLVs) refer to airborne concentrations of substances and represent conditions under which it is believed that nearly all workers may be repeatedly exposed day after day without adverse health effects. These exposure levels are based on animal studies. With these and with all such exposure standards, there is uncertainty, and not a guarantee that adverse health will not result from exposure to these levels of chemicals in the air.

There are other related terms and abbreviations that may be encountered. STELs, which are Short-Term Exposure Levels (15 minutes), are based on the idea that a short-term exposure to certain levels of certain chemicals may be allowed. For the vast majority of chemicals, there is simply not enough toxicological data (information from studies of the harmful effects of chemicals) to warrant or establish a STEL. TWA stands for Time-Weighted Average, which is based on the idea that exposure to levels of chemicals above the Threshold Limit Values are allowed so long as the employee is subjected to periods of time when the exposure to levels of chemicals below the Threshold Limit Values during the workday. Biological Exposure Indices (BEIs) are reference values intended as guidelines for the evaluation of potential health hazards in the practice of industrial hygiene. BEIs represent the levels of determinants which are most likely to be observed in specimens collected from a healthy worker who has been exposed to chemicals to the same extent as a worker with some inhalation exposure to the TLV.


For more information about health effects of chemicals, try the following government-sponsored websites:

healthfinder - Department of Health and Human Services' gateway to medical journals, news, databases, libraries, state agencies, educational sites, organizations, and support groups

National Institutes of Health - federal health information resources, clinical-trial databases, consumer health publications, and an index of health conditions being investigated by the

National Library of Medicine features MedLine, a free database of citations and abstracts from 3,900 medical journals


Facility owners and operators can make decisions about what amounts of chemicals will be kept on-site and minimize those amounts. One option is having a "just-in-time" inventory, which means getting more frequent deliveries of small amounts of chemicals rather than having larger amounts in fewer deliveries. There is a trade-off of sorts in making this decision, and communities want to weigh whether the increase in deliveries and traffic, therefore increased transportation accident risk, is worth asking a facility to change its operations. Generally speaking, the risks to the community from a chemical spill during the transportation of chemicals are larger than the risks to the community from a chemical spill at the facility. Most facilities have good containment and emergency response procedures if they comply with the different environmental regulations. But the trained staff at a facility and the containment designed to handle a chemical spill is not available at a truck delivering chemicals if there is a mishap along the delivery route. Vehicle accidents are a fact of life, and even the most responsible driver can collide with another vehicle, and not be at fault. Also, congested traffic conditions can make it difficult for emergency responders to respond.

Another option available to facility operators is to find less toxic chemicals as alternatives or chemicals that will not have "off-site consequences" when spilled. A classic example of this is the Chlorine used at municipal water wells. Chlorine is a very deadly chemical, and a spill or release of large amounts of Chlorine from a tank can be hazardous for many miles from the spill. Some cities have substituted other chemicals, Calcium Hypochlorite, or Calcium Nitrate Solutions, for the Chlorine. This type of substitution of less dangerous chemicals to reduce or eliminate risks to the community is exactly the type of reasoning that EPCRA asks of the public, facility operators, and planning agencies. However, EPCRA makes these choices strictly voluntary.


When planning to open a new facility, making chemical process changes at an existing facility, or even rearranging an existing facility, facility owners and operators should consider the compatibility of the various chemicals that may be stored next to each other at the facility. This is important because the inadvertent mixing of incompatible chemicals can cause fires, explosions, poison gases to form, and other unexpected outcomes. It is important to consider what possible mixing of chemicals might occur in the event of a spill, fire, or hazardous materials incident.

To help understand potential reactions where more than one chemical may be involved in a spill scenario, the Chemical Reactivity Worksheet has been developed. It can be found on the web at:, or at This can be downloaded from the Internet. It includes a database of reactivity information for more than 4,000 common hazardous chemicals. The database includes information about the special hazards of each chemical and about whether a chemical reacts with air, water, or other materials. It also includes a way to virtually "mix" chemicals to find out what dangers could arise from accidental mixing. If there is concern about the compatibility of chemicals at a facility, the Chemical Reactivity Worksheet will help determine what could go wrong.


Just because a facility does not have to file Tier Two Reports does not mean that the chemicals on-site would not pose a risk to the adjacent community in the event of a spill. The 10,000 pound threshold for OSHA chemicals (non-EHS) is an effort to make "one shoe fit all sizes," and that may not always work. Chemicals have different toxicity levels. Also, a facility can keep chemicals at levels close to but never quite at the threshold reporting amounts. There is also continued debate about what the proper reporting and planning thresholds for different chemicals should be as more information on toxicity is developed.

Just because a facility files Tier Two Reports does not mean that it has enough chemicals on-site to pose a threat to the nearby community or passersby if there is a spill or release.

For example, if a facility uses sulfuric acid in its processes, and it has a total of 500 pounds of sulfuric acid on-site at any time during a calendar year, it has to file certain EPCRA information and reports (including Tier Two Reports) with the fire department, LEPC, and the SERC. But 500 pounds of sulfuric acid could fit in one or two 55-gallon drums. And a spill of a drum of sulfuric acid would not likely affect people off-site, or have "off-site consequences." But the facility would have to responsibly plan for, and deal with, such a spill. Workers also have a right to know about the hazards they are dealing with and how to handle an emergency situation.

Sulfuric acid is in a special EPCRA category, Section 302, or Extremely Hazardous Substances (EHS). The EHS category has its own special requirements. EPA has developed a list of chemicals designated as EHS chemicals. (See the EHS discussion - click) One of the requirements created for a facility is the preparation of a facility emergency plan, and a determination of how far away from the facility the chemical could travel and the effects a chemical spill could have on the area nearby. This is called an "off-site consequence analysis." While a facility having 500 pounds of sulfuric acid on-site would not pose a particular threat to areas beyond the facility boundary, a facility with large amounts of sulfuric acid, thousands of pounds, or million of pounds, of sulfuric acid could affect quite a large area in the event of a large spill of chemicals. To determine what the risk is from a release of chemicals from a facility, a person will need to look at the actual amounts, and kinds, stored on-site at a facility.

The LEPC must create an emergency plan that identifies the facilities that are subject to EHS planning requirements within the emergency planning district, and this comprehensive emergency plan is required to determine "the area or population likely to be affected" by a chemical spill. So the off-site consequence analysis of the potential spill of chemicals from facilities should be determined for the creation of this comprehensive emergency plan created by the LEPC. If the LEPC requests the off-site consequence analysis information from a facility, EPCRA requires the facility owner or operator to "promptly" provide this data. Sometimes the LEPC needs to be reminded by the public to gather this information. In some areas, the LEPC will make these calculations.

Bear in mind that a business can make decisions to store less chemicals on-site or change its processes to use different chemicals that are not as hazardous if spilled. EPCRA does not provide authority to make a business or facility store less or make these changes, but public awareness and pressure can make a difference.

By filing the appropriate EPCRA reports, a facility has to think in terms of what to do in the event something goes wrong. After all, accidents do happen, but not everyone thinks about what can go wrong because no-one plans to have an accident. They just happen. EPCRA preparation and forethought causes facilities to plan for such incidents, train its employees, and develop the appropriate emergency response procedures. It is in a community's interest that this preparation take place, because emergency planning and preparedness helps protect workers, emergency responders, nearby businesses and business property, and the public and its private and public property. If the facility is in compliance with the EPCRA laws, it is inherently safer than a facility that is not in compliance with EPCRA.

If the public believes that facilities could find ways to reduce the amounts of chemicals on-site and reduce the risk of an off-site consequence, the public should ask the Local Emergency Planning Committee (LEPC) to discuss the matter with the facility. An individual may request that this be put on the LEPC meeting agenda for discussion. An individual or community group certainly has the right to attend these LEPC meetings and state the concerns, or write the LEPC a letter, or both. An individual or community group may also approach the facility, but should remember to be polite and professional. The facility is also a community member.


Land use decisions are commonly handled by planning and zoning departments and planning and zoning boards. These planning and zoning boards determine where the various types of homes, apartment buildings, stores, businesses, farms, industries that use chemicals, gas stations, and every other use of land will be.

These land use decisions should be made after using and considering EPCRA chemical information. It makes sense to avoid putting facilities that must store large amounts of hazardous chemicals on-site next to residential communities, hospitals, schools, sports arenas, and similar public facilities. Keeping these incompatible land uses apart avoids creating unneeded, additional risks. When planning and zoning boards make facility siting decisions, they should examine the off-site consequence scenarios to make sure the facility's siting will not put other areas at an undue risk. This should be done before the facility is built.

Not all planning and zoning departments/boards consider the consequences of chemical use of storage before zoning in a facility. This is a mistake. The proximity of medical facilities with the capability of dealing with a chemical accident should also be a consideration. It is not good planning to put the facility with the hazardous chemicals far away from the place or places that provide medical attention in the event of a chemical spill or accident. The availability of adequate emergency response should also be a key consideration. Few firefighting departments relish having to evacuate masses of people, especially residential areas (no set time of arrival or departure) during an encroaching chemical plumb. This "setup" is inherently dangerous for both residents and the emergency responders.

The planning and zoning boards should also make sure that chemicals that are inherently incompatible (cannot be mixed without causing a dangerous chemical reaction) are not sited near each other. For example, corrosives (acids) and fuels are not to be stored near each other at a facility. So putting a facility that will store large amounts of corrosives next to a facility that will store large amounts of gasoline or propane would not be a good idea. It won't do any good for these two types of facilities if they take the proper precautions to keep these chemicals apart at their own individual facilities, only to have these incompatible chemicals sited or placed near each other inadvertently by planning and zoning boards. Once a large chemical storage tank is sited, built, and filled, it is an expensive and unwanted expense to have to move them again because a planning and zoning board did not take the extra risk or hazards into account. It is potentially even more expensive if a chemical incident occurs.

It also makes sense to not put facilities that will have large amounts of hazardous chemicals on-site into an area with poor access for transportation. In the event of a spill, there needs to be several escape routes away from the spilled chemicals in the event of an evacuation. Of course, the firefighters and emergency responders need to be able to get to the spill scene to help, and having poor access will not help them either. A transportation incident could block an area with poor access and not allow for any necessary evacuation. Proper and adequate planning is necessary for a safe community.


The MSDS is the building block that leads to Tier Two Reporting requirements (chemical storage) and understanding the chemical hazards. The Tier Two Reports and facility emergency plans are used to make the regional emergency plan. The emergency notification sets the appropriate emergency response in motion. The written followup report is used by the public, and others, in helping to determine what effects the "release" had and what may be needed to provide medical attention and possibly decontamination.