Prevention of fires and explosions

Prevention of fires and explosions

Klaus Kuhl and Raluca Stepa, Kooperationsstelle Hamburg IFE GmbH, Germany



Fire can occur when flammable material, oxygen and sufficient ignition energy are available. Explosion depends on an atmosphere of a mixture of flammable material with oxygen. The best approach to prevent fires and explosions is to substitute or minimise the use of flammable material. If that is not possible it is important to avoid effective sources of ignition. The manufacturing, processing or storage of explosives is not covered in this article.


According to the International Association for the Study of Insurance Economics the direct costs of fires and explosions range between 0.07 and 0.26 percent of the Gross Domestic Product and the number of fire deaths varies between 20 in Slovenia and 660 in France, according to figures from 2005 [1] .

Fires and explosions in industrial structures and plants may not only lead to losses and damages but may also hamper the functioning of the economy. In Germany three explosions occur daily on average according to the accident insurance company for the chemical industry and similar sectors, whereby fortunately most of them do not cause bigger problems due to protective measures being in place [2] . Small workshops like garages have a high risk of fires and explosions because they use highly volatile hydrocarbons for spray painting and cleaning purposes. In Schleswig-Holstein (Germany) alone four garages experienced large fires between 2009 and 2010 and one had to close down afterwards.

Fires and explosions

Fire is a rapid oxidation of material releasing heat, light and various chemical products. The fire triangle describes the conditions that have to be met in order a fire can start: (1) flammable material, (2) oxygen, (3) energy to ignite the fire.

All material capable of an exothermic oxidation reaction has to be considered as flammable. This can be:

  • gases such as butane, propane, methane, carbon monoxide, hydrogen,
  • liquids such as fuels, solvents, oils, greases, paints and thinners,
  • solids such as wood, coal, plastics, metals, food.

Oxygen is usually available in sufficient quantities in our air to get a fire started and to sustain it. Fires may however start much easier and may be more powerful in terms of flame volume and released energy, if the oxygen content of the surrounding atmosphere is increased, e.g. when an oxygen cylinder leaks or bursts or when oxygen releasing substances (e.g. peroxides) are present.

The needed ignition energy can be very low (usually with gases) and can be quite high, which is usually the case with solids. Liquids are often somewhere in between. However the ignition of solids or aerosols depends also on the particle size: fine dusts of e.g. aluminium or flour mixed with air can explode easily.

An explosion is a rapid increase in volume and release of energy in an extreme manner, usually with the generation of high temperatures and the release of gases. An explosion creates a shock wave [3] . Does the created shock wave exceed the velocity of sound we talk about a detonation; is the velocity lower the term deflagration is used [4] .

Occupational safety and health management

Employers have a duty to ensure the safety and health of workers in every aspect related to the work and they have to provide the necessary organisation and means. Starting with allocating responsibilities the health and safety personnel has to have the necessary knowledge to conduct a risk assessment regarding possible fire and explosion hazards and to select related measures. If appropriately qualified staff is not available within the company, the employer has to contract an outside expert [5] .

On determining the company processes, fire risks as well as fire prevention and fighting measures have to be considered already in the design phase. In collaboration with architects and fire prevention experts this may include: indicating fire compartments, separation of special units, extinguisher systems and escape routes.

Ensuring qualification and further education of all employees involved in fire prevention and fire-fighting tasks is another important management issue. This has to include regular fire drills and should also involve demonstrations of how easily fires can develop presented by the fire brigade or related institutions. Employees should be given the opportunity to not only develop their knowledge but to also bring in their experience. This is all the more important as also unplanned and unforeseeable dangerous situations and the behaviour of workers need to be considered. However in this aspect it is also of foremost importance that all superiors set a good example and always follow the rules themselves.

Good management should also seek advice from outside experts where necessary, provide for effective monitoring, allow opportunities to learn from experience by analysing fires and risky situations and thus create continuous improvement processes. Finally all important aspects should be documented for further reference. In order to have a comprehensive structure, employers should consider to implement an OSH management system, this could even be integrated into a quality and environment management system so as to make use of synergy effects.

In case of higher risks it may be necessary to put a permission system in place, only giving specifically trained people access to sensitive and dangerous areas. Coordinating panels involving e.g. contractors on the premises have to be set up and means and ways of communication between all stakeholders need to be established carefully.

The situation in small and medium enterprises can be quite different from that of larger firms. These may be service companies doing e.g. maintenance work for larger companies or individual customers (e.g. garages). From their point of view it is important to have always the right contact persons, to be involved in the client’s risk assessment processes, to be always up to date regarding developments of the contractor’s buildings and machines, to have the right equipment and to receive sufficient training.

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Identification of fire and explosion risks

Companies have to conduct risk assessments. A risk assessment is a careful examination of what, in any institution, could cause harm to people, so that one can judge whether there are enough precautions in place or more is needed to prevent harm. It involves identifying the hazards present in any undertaking (whether arising from work activities or from other factors, e.g. the layout of the premises) and then evaluating the extent of the risks involved, taking into account existing precautions [6] .

A fire hazard can harm workers and the public not only by causing burns but also by heat, fire gases, smoke and weakening structures and it may cause explosions if explosive atmospheres can develop.

Of foremost importance regarding any fire and explosion risk assessment, is to identify related problematic substances in the company. These could be flammable liquids, gases, aerosols, solids, dusts, substances that can develop spontaneous ignition (e.g. textiles with decomposing greases and fats), substances that develop flammable gases on contact with water or other chemicals, explosives, oxidising substances (e.g. peroxides). It has also to be established as to whether there are any working processes that may release any of the above mentioned substances (e.g. dusts, mixture of chemicals). For all the identified substances all relevant parameters, like flash points, vapour pressure, calorific value, explosion limits, etc. should be established.

It is also necessary to clarify, who is working with these substances, in which processes for how long. Not only the normal work procedures have to be analysed but also servicing, test runs, malfunctioning of machines and plants as well as unauthorized access.

Are there effective ignition sources like open flames and high temperatures available or may they develop during work processes? Such ignition sources can be:

  • Thermal energy: combustion engines, open fire, hot surfaces, welding sputters, laser
  • Electric energy: short circuits, electric arcs, electromagnetic radiation, lightning, electrostatic, heat developed by currents
  • Mechanical energy: friction, ultrasound, compression, sparks from tools, grinding
  • Chemical energy: spontaneous heating or igniting, catalytic reactions, accelerating exothermal reactions

On having gathered and analysed all relevant information, the risk assessment team has to evaluate the extent of the risks involved. A high risk is indicated by larger amounts of flammable or oxidising substances and by a certain probability of a fire outbreak whereby a fast spread of the fire or big amounts of smoke and heat can be expected. This may be the case for sectors like: petro chemistry, chemical industry, electroplating, light metal processing, printing industry, rubber industry, wood processing, mills and silos, garages, food industry.


If problematic substances, as specified in the preceding chapter, exist in the company, the employer has to establish as to whether the development of an explosive atmosphere is possible. Such an atmosphere is defined as a mixture of oxygen with flammable substances, whereby this can include not only gases or aerosols from liquids but also particles from solid matter. For example a cloud of dust from flour or other biologic material, as well as from metal fines, can also explode and cause severe damage [7] . In the next step it has to be established if this atmosphere can develop in such amounts that it would need special measures.


The risk assessment has also to consider the organisation of the company, any individuals identified as being particularly at risk and the fire or explosion measures already in place. It has to be concluded whether these measures are sufficient or would need changes and improvements. The implementation may mean making changes to the organisation and working procedures, working environment, equipment and products used; training management and staff; and improving communications. The findings have to be recorded.


The adoption of any policies and measures should always be carefully planned, and carried out with consultation of the workforce and their representatives as a key component of success. This should include coordination and communication between contractor and possible service company personnel. The general principle, also laid down in the resp. EU directives, is that risks should be prevented at source and that work organisation, tasks, equipment and tools should be adapted to workers in order to eliminate and reduce risks. Measures should follow the prevention hierarchy:

  1. elimination of risks
  2. substitution e.g. of dangerous and flammable substances
  3. collective control measures like avoidance of effective ignition sources
  4. individual control like personal protective equipment

There have to be periodic reviews to check that measures, policies and procedures remain appropriate and are working. They have to be revised if necessary.

The following table shows some possible preventive measures.

Table 1: Risks and preventive measures regarding fire

Source: Adapted from AGS, 2010 [5]

Preventive measures regarding explosions

These measures would firstly have to focus on the avoidance of explosive atmospheres mainly by substituting or reducing flammable and oxidising substances (see table 1). Also mixtures with inert gases can sometimes be applied for dilution. If that is not possible, the employer has to assign special clearly marked and cordoned off zones (see table below) according to the ATEX directives [8] [9] . “An international standard, BS EN 60079/10, explains the basic principles of area classification for gases and vapours, and its equivalent for dusts was published in 2002 as BS EN 61241/3.” [10] . After assigning and indicating the zones, the next step is to ensure that effective ignition sources are avoided by using specified equipment/machines for the different zones. Equipment is categorised in 1, 2 or 3 depending on the zone number where it is intended to be used (0/20, 1/21, 2/22).

Table 2: Zones according to ATEX

Source: Adapted from HSE, 2010 [10]

If it is still not possible to effectively prevent the ignition of the explosive atmospheres, the employer has to introduce constructive measures that limit the effects of explosions to a harmless level. These measures can be: explosion-resistant construction, explosion venting (e.g. bursting discs), explosion suppression (rapid injection of extinguishing agents) or explosion isolation.

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All these steps have to be documented, put into an explosion protection document and shown to the authorities on demand.

Measures in case of an accident

Especially the large fires and explosions in firms (e.g. explosions in a chemical company in Rotterdam in early 2011) indicate how important it is to have safe systems in place. On the other hand it also shows that it is equally important to be prepared when accidents happen. Such plans should consist of a first aid organisation, of fire fighting and evacuation plans and of related alarm plans. This should be established based on the company’s risk assessment and involve appropriately qualified staff or consultants. Exercises should be conducted regularly.


On the basis of the «Framework directive» a series of individual directives were adopted, especially relevant for this topic are the following:

  • Directive 1999/92/EC – risks from explosive atmospheres of 16 December 1999 on minimum requirements for improving the safety and health protection of workers potentially at risk from explosive atmospheres (15th individual Directive within the meaning of Article 16(1) of Directive 89/391/EEC [11] .
  • Directive 92/58/EEC – safety and/or health signs of 24 June 1992 on the minimum requirements for the provision of safety and/or health signs at work (ninth individual Directive within the meaning of Article 16 (1) of Directive 89/391/EEC)
  • Directive 98/24/EC – risks related to chemical agents at work of 7 April 1998 on the protection of the health and safety of workers from the risks related to chemical agents at work (fourteenth individual Directive within the meaning of Article 16(1) of Directive 89/391/EEC)

These directives including the framework directive had to be transformed into the national legislation of the member states.

There are two so called ATEX directives, one for the manufacturer and one for the user of the equipment: the ATEX 95 equipment directive 94/9/EC, Equipment and protective systems intended for use in potentially explosive atmospheres and the ATEX 137 workplace directive 99/92/EC, Minimum requirements for improving the safety and health protection of workers potentially at risk from explosive atmospheres.

Acrylamide and Cancer Risk

What is acrylamide?

Acrylamide is a chemical used primarily to make substances called polyacrylamide and acrylamide copolymers. Polyacrylamide and acrylamide copolymers are used in many industrial processes, such as the production of paper, dyes, and plastics, and in the treatment of drinking water and wastewater, including sewage. They are also found in consumer products, such as caulking, food packaging, and some adhesives.

Acrylamide is also found in some foods. It can be produced when vegetables that contain the amino acid asparagine, such as potatoes, are heated to high temperatures in the presence of certain sugars (1, 2). It is also a component of tobacco smoke.

How are people exposed to acrylamide?

Food and cigarette smoke are the major sources of acrylamide exposure for people in the general population (3, 4).

The major food sources of acrylamide are French fries and potato chips; crackers, bread, and cookies; breakfast cereals; canned black olives; prune juice; and coffee.

Acrylamide levels in food vary widely depending on the manufacturer, the cooking time, and the method and temperature of the cooking process (5, 6). Decreasing cooking time to avoid heavy crisping or browning, blanching potatoes before frying, not storing potatoes in a refrigerator, and post-drying (drying in a hot air oven after frying) have been shown to decrease the acrylamide content of some foods (7, 8).

People are exposed to substantially more acrylamide from tobacco smoke than from food. People who smoke have three to five times higher levels of acrylamide exposure markers in their blood than do non-smokers (9). Exposure from other sources is likely to be significantly less than that from food or smoking, but scientists do not yet have a complete understanding of all sources of exposure. Regulations are in place to limit exposure in workplaces where acrylamide may be present, such as industrial settings that use polyacrylamide and acrylamide copolymers.

Is there an association between acrylamide and cancer?

Studies in rodent models have found that acrylamide exposure increases the risk for several types of cancer (10–13). In the body, acrylamide is converted to a compound called glycidamide , which causes mutations in and damage to DNA. However, a large number of epidemiologic studies (both case-control and cohort studies) in humans have found no consistent evidence that dietary acrylamide exposure is associated with the risk of any type of cancer (9, 14). One reason for the inconsistent findings from human studies may be the difficulty in determining a person’s acrylamide intake based on their reported diet.

The National Toxicology Program’s Report on Carcinogens considers acrylamide to be reasonably anticipated to be a human carcinogen, based on studies in laboratory animals given acrylamide in drinking water. However, toxicology studies have shown that humans and rodents not only absorb acrylamide at different rates, they metabolize it differently as well (15–17).

Studies of workplace exposure have shown that high levels of occupational acrylamide exposure (which occurs through inhalation) cause neurological damage, for example, among workers using acrylamide polymers to clarify water in coal preparation plants (18). However, studies of occupational exposure have not suggested increased risks of cancer (19).

Are acrylamide levels regulated?

The U.S. Environmental Protection Agency (EPA) regulates acrylamide in drinking water. The EPA established an acceptable level of acrylamide exposure, set low enough to account for any uncertainty in the data relating acrylamide to cancer and neurotoxic effects. The U.S. Food and Drug Administration regulates the amount of residual acrylamide in a variety of materials that contact food, but there are currently no guidelines governing the presence of acrylamide in food itself.

What research is needed to better understand whether acrylamide is associated with cancer in people?

Additional epidemiologic studies in which acrylamide adduct or metabolite levels are serially measured in the same individuals over time (longitudinal cohorts) are needed to help determine whether dietary acrylamide intakes are associated with increased cancer risks in people. It is also important to determine how acrylamide is formed during the cooking process and whether acrylamide is present in foods other than those already tested. This information will enable researchers to make more accurate and comprehensive estimates of dietary exposure. Biospecimen collections in cohort studies will provide an opportunity to examine biomarkers of exposure to acrylamide and its metabolites in relation to the subsequent risk of cancer.

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Where can people find additional information about acrylamide?

For more information about acrylamide in food, contact the FDA at 1-888-SAFEFOOD (1-888-723-3366) or visit their Acrylamide page.

Selected References

Stadler RH, Blank I, Varga N, et al. Acrylamide from Maillard reaction products. Nature 2002; 419(6906): 449–450. doi:10.1038/419449a.

Mottram DS, Wedzicha BL, Dodson AT. Acrylamide is formed in the Maillard reaction. Nature 2002; 419(6906):448–449. doi:10.1038/419448a.

Urban M, Kavvadias D, Riedel K, Scherer G, Tricker AR. Urinary mercapturic acids and a hemoglobin adduct for the dosimetry of acrylamide exposure in smokers and nonsmokers. Inhalation Toxicology 2006; 18(10):831–839.

Çebi A. Acrylamide Intake, Its Effects on Tissue and Cancer. In: Gökmen V, editor. Acrylamide in Food. Analysis, Content and Potential Health Effects. London: Academic Press, 2016.

Tareke E, Rydberg P, Karlsson P, Eriksson S, Tornqvist M. Analysis of acrylamide, a carcinogen formed in heated foodstuffs. Journal of Agricultural and Food Chemistry 2002; 50(17):4998–5006.

Mojska H, Gielecinska I, Szponar L. Acrylamide content in heat-treated carbohydrate-rich foods in Poland. Roczniki Panstwowego Zakladu Higieny 2007; 58(1):345–349.

Kita A, Brathen E, Knutsen SH, Wicklund T. Effective ways of decreasing acrylamide content in potato crisps during processing. Journal of Agricultural and Food Chemistry 2004; 52(23):7011–7016.

Skog K, Viklund G, Olsson K, Sjoholm I. Acrylamide in home-prepared roasted potatoes. Molecular Nutrition and Food Research 2008; 52(3):307–312.

Virk-Baker MK, Nagy TR, Barnes S, Groopman J. Dietary acrylamide and human cancer: a systematic review of literature. Nutrition and Cancer 2014;66(5):774-790.

Dearfield KL, Abernathy CO, Ottley MS, Brantner JH, Hayes PF. Acrylamide: Its metabolism, developmental and reproductive effects, genotoxicity, and carcinogenicity. Mutation Research 1988; 195(1):45–77.

Dearfield KL, Douglas GR, Ehling UH, et al. Acrylamide: A review of its genotoxicity and an assessment of heritable genetic risk. Mutation Research 1995; 330(1–2):71–99.

Friedman M. Chemistry, biochemistry, and safety of acrylamide. A review. Journal of Agricultural and Food Chemistry 2003; 51(16):4504–4526.

National Toxicology Program. Toxicology and carcinogenesis studies of acrylamide (CASRN 79-06-1) in F344/N rats and B6C3F1 mice (feed and drinking water studies). National Toxicology Program technical report series 2012; (575):1-234.

Lipworth L, Sonderman JS, Tarone RE, McLaughlin JK. Review of epidemiologic studies of dietary acrylamide intake and the risk of cancer. European Journal of Cancer Prevention 2012; 21(4):375-386.

Fuhr U, Boettcher MI, Kinzig-Schippers M, et al. Toxicokinetics of acrylamide in humans after ingestion of a defined dose in a test meal to improve risk assessment for acrylamide carcinogenicity. Cancer Epidemiology Biomarkers and Prevention 2006; 15(2):266–271.

Fennell TR, Friedman MA. Comparison of acrylamide metabolism in humans and rodents. Advances in experimental medicine and biology 2005; 561:109-116.

Gargas ML, Kirman CR, Sweeney LM, Tardiff RG. Acrylamide: Consideration of species differences and nonlinear processes in estimating risk and safety for human ingestion. Food and chemical toxicology 2009; 47(4):760-768.

Mulloy KB. Two case reports of neurological disease in coal mine preparation plant workers. American Journal of Industrial Medicine 1996; 30(1):56–61.

Pelucchi C, La Vecchia C, Bosetti C, Boyle P, Boffetta P. Exposure to acrylamide and human cancer—a review and meta-analysis of epidemiologic studies. Annals of Oncology 2011; 22(7):1487-1499.


Escherichia coli (abbreviated as E. coli) are bacteria found in the environment, foods, and intestines of people and animals.

Most E. coli are harmless and are actually an important part of a healthy human intestinal tract. However, some E. coli can cause diarrhea, urinary tract infections, respiratory illness, bloodstream infections, and other illnesses. The types of E. coli that can cause illness can be transmitted through contaminated water or food, or through contact with animals or people.

What are Shiga toxin-producing E. coli?

Some kinds of E. coli bacteria cause disease when they make a toxin called Shiga toxin. The bacteria that make these toxins are called “Shiga toxin-producing E. coli,” or STEC for short.

How can I prevent a STEC infection?

  • Know your chances of getting food poisoning. People with higher chances for foodborne illness are pregnant women, newborns, children, older adults, and those with weak immune systems, such as people with cancer, diabetes, or HIV/AIDS.
  • Practice proper hygiene, especially goodhandwashing.
    • Wash your hands thoroughly after using the bathroom and changing diapers.
    • Wash your hands thoroughly before and after preparing or eating food.
    • Wash your hands thoroughly after contact with animals or their environments (at farms, petting zoos, fairs, even your own backyard).
    • Wash your hands thoroughly before preparing and feeding bottles or foods to an infant or toddler, before touching an infant or toddler’s mouth, and before touching pacifiers or other things that go into an infant or toddler’s mouth.
    • Keep all objects that enter infants’ and toddlers’ mouths (such as pacifiers and teethers) clean.
    • If soap and water aren’t available, use an alcohol-based hand sanitizer with at least 60% alcohol (check the product label to be sure). These alcohol-based products can quickly reduce the number of germs on hands in some situations, but they are not a substitute for washing with soap and running water.

    Wash fruits and vegetables well under running water, unless the package says the contents have already been washed.

  • Cook meats thoroughly:
    • To kill harmful germs, cook beef steaks and roasts to an internal temperature of at least 145°F (62.6˚C) and allow to rest for 3 minutes after you remove meat from the grill or stove.
    • Cook ground beef and pork to a minimum internal temperature of 160°F (70˚C).
    • Always use a food thermometer to check that the meat has reached a safe internal temperature External because you can’t tell whether meat is safely cooked by looking at its color.
  • Don’t cause cross-contamination in food preparation areas. Thoroughly wash hands, counters, cutting boards, and utensils after they touch raw meat.
  • Avoidraw milk, unpasteurized dairy products, and unpasteurized juices (such as fresh apple cider).
  • Don’t swallow water whenswimming and when playing in lakes, ponds, streams, swimming pools, and backyard “kiddie” pools.

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