The Dangerous Substances and Explosive Atmospheres Regulations (DSEAR) are in place to ensure that the risk of ignited events is appropriately managed at establishments that store and/or process explosive substances. The main focus of DSEAR is preventing ignition of flammable atmospheres, but by placing too much faith on preventative measures, we can lose focus on how the impact of incidents should be managed in case they do happen. Effective risk management is achieved by creating a balance between what we have in place to prevent, control, and mitigate the consequences of an incident.
Aspects that are often neglected due to the primary focus being on hazardous areas are those that provide the potential for ignited incidents to escalate, for example due to poor facility layout. Adequate separation of vessels containing flammable or combustible substances, and segregation of these from buildings, site boundaries, incompatible materials and prevention of ignition sources all reduce the risk of escalation and reduce the potential for harm by improving the escape probability of nearby personnel. Information on separation and segregation of process areas and buildings from ignition sources is provided across industry guidance, but the relevancy of guidance depends on the establishment. For those establishments that have a number of dangerous substances, each piece of appropriate guidance should be identified and integrated into the overall arrangements for risk management. Where there are substances in several process areas and space on site is limited, meeting the guidance can bring some challenges in terms of practicability.
The following sections outline some key considerations to help organisations of different types reduce escalation potential.
The influence of separation and segregation will be compromised if combustible materials are present in hazardous areas. This doesn’t just apply to other dangerous substances, but to materials such as waste, oily rags and even vegetation that are left to accumulate.
Guidance says that compressed gas cylinders should preferentially be stored outside in a segregated area. As described above, vegetation should be managed and removed from within three meters of the area. Where a dedicated outdoor facility for storing gas cylinders is not an option, appropriate ventilation and a bespoke storage facility should be provided, again with a minimum distance of three metres from combustible materials and ignition sources.
It is important to bear in mind that guidance stipulates that compressed gas cylinders are never truly empty unless they are new or de-valved. Guidance on the storage of gas cylinders should therefore be followed whether or not they are thought to be empty.
In managing flammable atmospheres, the importance of the appropriate management of dust should not be underestimated. Dusty areas may extend well beyond the source of the dust unless extraction is installed, and should a fire break out in a facility where significant quantities of dust are left to accumulate then the fire could escalate rapidly. Installing a system to segregate storage/process areas from the rest of the facility or limit the extent of dust clouds using ventilation is therefore good practice to limit the extent of a fire.
Where space is an issue, separation may be provided by the use of physical fire-resistant barriers. These should be appropriately designed, manufactured and positioned for their specific requirements.
It is essential to remember that DSEAR compliance does not stop at hazardous area classification. Compliance with the DSEAR regulations requires a systems approach to risk management, from the processes in place to prevent and reduce hazardous areas, through to controlling and mitigating the consequences of an event should it occur. Investing in the right balance can provide more peace of mind in protecting people, the environment and assets.
Jenny Hill & Carolyn Nicholls