In our experience within the manufacturing industry, the most relevant standard is NFPA 654. The goal of the NFPA 654 standard is to provide safety measures to prevent and mitigate fires and explosions in facilities that handle combustible particulate solids.
This standard applies to all phases of the manufacturing, processing, blending, conveying, repackaging, and handling of combustible particulate solids or hybrid mixtures, regardless of concentration or particle size, where the materials present a fire or explosion hazard. The owners or operators of affected facilities are responsible for implementing the requirements.
NFPA 652 – Standard on the Fundamentals of Combsutible Dust
NFPA 654 – Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing and Handling of Combustible Particulate Solids
NFPA 68 – Guide for Venting of Deflagrations
NFPA 69 – Standard on Explosion Prevention Systems
NFPA 499 – Recommended Practice for the Classification of Combustible Dusts and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas
NFPA 61 – Standard for the Prevention of Fires and Dust Explosions in Agricultural and Food Processing Facilities
NFPA 484 – Standard for Combustible Metals
NFPA 655 – Standard for Prevention of Sulfur Fires and Explosions
NFPA 664 – Standard for the Prevention of Fires and Explosions in Wood Processing and Woodworking Facilities
The directive is actually divided into two branches, one which applies to the manufacturer or the equipment involved, and another which applies to the users and the workplace environment in which the equipment is employed.
1) Directive 99/92/EC (also known as the ‘ATEX Workplace Directive’) contains minimum requirements for improving the health and safety protection of workers potentially at risk from explosive atmospheres.
2) Directive 2014/34/EU (also known as ‘the ATEX Equipment Directive’) contains the laws of Members States concerning equipment and protective systems intended for use in potentially explosive atmospheres.
Explosive atmospheres can be caused by flammable gases, mists or vapours or by combustible dusts. If there is enough of the substance, mixed with air, then all it needs is a source of ignition to cause an explosion.
Explosions can cause loss of life and serious injuries as well as significant damage. Preventing releases of dangerous substances, which can create explosive atmospheres, and preventing sources of ignition are two widely used ways of reducing the risk. Using the correct equipment can help greatly in this.
Equipment and protective systems intended for use in explosive atmospheres
The aim of Directive 94/9/EC is to allow the free trade of ‘ATEX’ equipment and protective systems within the EU by removing the need for separate testing and documentation for each Member State.
Manufacturers and suppliers (or importers, if the manufacturers are outside the EU) must ensure that their products meet essential health and safety requirements and undergo appropriate conformity procedures. This usually involves testing and certification by a ‘third-party’ certification body (known as a Notified Body) but manufacturers/suppliers can ‘self-certify’ equipment intended to be used in less hazardous explosive atmospheres. Once certified, the equipment is marked by the ‘EX’ symbol to identify it as such.
Certification ensures that the equipment or protective system is fit for its intended purpose and that adequate information is supplied with it to ensure that it can be used safely.
The Dangerous Substances and Explosive Atmospheres Regulations 2002 (DSEAR) place duties on employers to eliminate or control the risks from explosive atmospheres in the workplace.
In DSEAR, an explosive atmosphere is defined as a mixture of dangerous substances with air, under atmospheric conditions, in the form of gases, vapours, mist or dust in which, after ignition has occurred, combustion spreads to the entire unburned mixture.
Many workplaces may contain, or have activities that produce, explosive or potentially explosive atmospheres. Examples include places where work activities create or release flammable gases or vapours, such as vehicle paint spraying, or in workplaces handling fine organic dusts such as grain flour or wood.
DSEAR requires employers to eliminate or control the risks from dangerous substances. In addition to the general requirements, the Regulations place the following specific duties on employers with workplaces where explosive atmospheres may occur.
Employers must classify areas where hazardous explosive atmospheres may occur into zones. The classification given to a particular zone, and its size and location, depends on the likelihood of an explosive atmosphere occurring and its persistence if it does. Schedule 2 of DSEAR contains descriptions of the various classifications of zones for gases and vapours and for dusts.
Areas classified into zones must be protected from sources of ignition. Equipment and protective systems intended to be used in zoned areas should be selected to meet the requirements of the Equipment and Protective Systems Intended for Use in Potentially Explosive Atmospheres Regulations 1996. Equipment already in use before July 2003 can continue to be used indefinitely provided a risk assessment shows it is safe to do so.