While dealing with harmful and chemical substances, there exists a body of regulations that must be followed. However, depending on the characteristics of the substance, different regulations must be followed by employers. COSHH and DSEAR are similar as they require employers to fully assess and control the hazards and risks that result while handling, using, storing, or transporting hazardous or dangerous substances. 


The Dangerous Substances and Explosive Atmosphere Regulations (DSEAR) (SI 2002 No.2776) is a statutory body that establishes obligations on the employer to protect their employees and the general public from the dangerous substances being used in the course of the business. It is the primary legislation applied to control substances that can cause fires and explosions in the workplace. DSEAR put into effect requirements from two European Directives: the Chemical Agents Directive (98/24/EC) and the Explosive Atmospheres Directive (99/92/EC). It complements the risk management required under the Management of Health and Safety at Work Regulations 1999 (SI 1999 No 3242). 

DSEAR applies when substances are classified as dangerous when they have the ability to injure or kill. These could be substances or mixtures of substances (referred to as preparations in DSEAR) that could create risks to people’s safety. They may also be explosive, spontaneously combustible, flammable, corrosive, oxidizing, or highly reactive. Such substances are not necessarily hard to find and may exist in most workplaces. Certain paints, nail polish removers, disinfectants, glues, solvents, and gases could potentially be explosive or flammable and as such may be classified as a dangerous substances.

The substances must be present in a workplace where dangerous substances are present, used, or produced. The work must be carried out by an employer (or self-employed person who is considered an employer for the purpose of the Regulations), a dangerous substance is present (or is liable to be present) at the workplace, the dangerous substance could be a risk to the safety of people as a result of fires, explosions or similar events (thermal runaway). Fires and other energetic events involving chemicals may have other harmful physical effects such as thermal radiation, overpressure effects, and oxygen depletion. Commencing June 2015, DSEAR also began to cover the risk caused by pressurized gases and corrosive substances Corrosive substances may cause damage to metal/metal-containing structures which could result in reduced structural integrity. DSEAR aims to limit such harmful effects.

To meet the criteria for classification as hazardous, a substance must fall within any physical hazard class (such as flammable) as laid down in the CLP Regulation (Classification, Labelling and Packaging under The European Chemicals Agency) as to whether or not the substance is classified under that regulation.

Many hazardous substances may also create health risks as they may be toxic or irritant. While DSEAR considers safety, these health risks are covered under the Control of Substances Hazardous to Health Regulations (COSHH).

Workplaces are defined as any premises or parts of premises used for work such as industrial and commercial premises. Houses and other domestic premises are also working premises if people are at work there.

Some DSEAR requirements deal specifically with explosive atmospheres (ATEX). These requirements do not apply to industries such as offshore oil and gas production. ATEX refers to procedures that control explosive atmospheres and the established standards of equipment and systems used. It is based on the European ATEX Workplace Directive (Directive 99/92/EC) on minimum requirements for improving the health and safety protection of workers potentially at risk from explosive atmospheres. The ATEX component of the DSEAR endorses requirements under the BIS legislation and the Equipment and Protective Systems Intended for Use in Potentially Explosive Atmospheres Regulations 1996.


Some examples of processes and activities covered by this regulation are the storage of petrol as a fuel for cars, boats, or horticultural machinery, the use of flammable gases, such as acetylene, for welding, or in general, in the workplace, the handling and storage of waste dusts in a range of manufacturing industries and the handling and storage of flammable wastes such as fuel oils. The use of flammable solvents in laboratories and the storage and display of flammable goods, such as paints, in shops are also covered by the regulation. 

Employer Duties

The regulation requires employers to assess the risk by identifying areas in the workplace that may be explosive atmospheres through risk assessments. This examination should be of the dangerous substances, the activities involving those substances, and the ways that those substances could harm people. If there is negligible or minimal risk to safety then there is no further action required. However, if risks exist, employers must comply with DSEAR requirements.

If these risks cannot be removed, those areas must be marked as separate zones based on the risk level and kept free of ignition sources through protective systems to control and reasonably reduce the severity of any incidents involving those substances. Ideally, the dangerous substance must be replaced with another less dangerous one, or the process of work may be changed to eliminate the hazard. The regulations refer to this as a substitution. Further DSEAR requires other control mechanisms to be followed. These include the reduction of the number of dangerous substances to a minimum, minimizing the release of dangerous substances, and collecting, containing, and removing any releases to a safe place. These controls should be appropriate for the risk level of the substance or activity.

 Additionally, DSEAR requires employers to have a mitigating process in place. These too must be consistent with the risk level of the substance in question. Employers must have emergency procedures in place in the event of a catastrophe such that all employees and members of the public that might be at risk can escape the area and emergency services will be contacted to contain the emergency. DSEAR also requires employers to regularly review and update all their safety measures. Employees themselves must also be aware of all the risks they are exposed to at their workplace and all the potential health concerns that come with it. They may also be trained to spot hazards and report it. Other mitigation processes may include reducing the number of employees exposed to the risk and providing all employees with protective equipment.

 With continued technological development, knowledge gaps exist, such as regarding the hazardous risk associated with some nanomaterials. In such circumstances, HSE recommends a precautionary approach to risk aversion through control strategies that aim to reduce exposure to substances that are hazardous to health.


The Control of Substances Hazardous to Health (COSHH) Regulations 2002 is the UK’s regulation to ensure safe use and control of hazardous substances. The COSHH regulations have been in place for more than 25 years, but the most recent was re-enacted in 2002 with amendments to the Control of Substances Hazardous to Work Regulations 1999. It is a statutory body, similar to DSEAR, that places requirements on employers to ensure all those in their workplace are protected from substances that are hazardous to health. The substances referred to could include fumes, chemicals, vapors, particles, and dust. These substances generally are dangerous to the environment, toxic, and have oxidizing and corrosive abilities. They could potentially also have long-term health hazards (ex. carcinogenic) or cause damage over time. Although more complicated viruses are termed hazardous, as in the definition in the previous section, more common substances such as paint and dust may also be harmful.


COSHH requires employers to reduce exposure to hazardous substances by determining risks through risk assessments, controlling them as well as regularly reviewing and updating safety measures in the workspace. To prevent exposure employers should try to avoid using a hazardous substance and find a safer alternative for it if that would be possible. If exposure cannot be prevented, control mechanisms must be installed. This is sufficient when the risk of harm is ‘as low as is reasonably practicable and exposure is below the Workplace Exposure Limit

The breach of COSHH regulations by an employer or employee is a crime that is punishable by an unlimited fine. It protects health by controlling the exposure of employees to hazardous substances.

Employer Duties

Employers are to limit and control the exposure of their employees or anyone in the workplace to hazardous substances by keeping the hazardous material in a chamber with limited access or by providing protective equipment such as PPE, if necessary. Employers must also provide information regarding working with the substance or activity to employees and instruct and train them to deal with a potential hazard in a safe manner. Merely presenting safety data sheets on a file is not sufficient to comply with the requirements.  Emergency procedures must be in place and COSHH risk assessments must be carried out. The use of hazardous substances doesn’t exceed the Workplace Exposure Limit (WEL). Additionally, employees working with hazardous substances or carrying out the activity must be supervised by the employer according to the regulations.

Employees too have responsibilities under the regulation to ensure a safe workplace. They must assist and support colleagues by abiding by the regulations specific to their workplace. They are to follow the procedure to stop accidents and any unnecessary exposure to the substance. They must also report and record all accidents regarding the substance and routinely keep up with the training provided to them.