Tetra Tech provided hazardous area classification studies across nine On-Site Electro Chlorination (OSEC) sites and a major sewage-treatment works for a large UK water company.
We were commissioned to provide Hazardous Area Classification studies for nine On-site Electro Chlorination (OSEC) sites and a large sewage treatment works operated by a large water company.
Our client was keen to ensure the classifications were up to date prior to embarking on equipment inspections, therefore setting clear demarcation for the inspection team and ensuring the equipment inventory was accurately collated.
Challenge
The Dangerous Substances and Explosive Atmospheres Regulations (DSEAR) contain specific requirements to demarcate hazardous from non-hazardous areas. As with many industries outside the normal high hazard oil, gas and chemical industries, guidance for Hazardous Area Classification can be difficult to find, be overly pessimistic or out of date.
Without relevant industry guidance, the justification of hazardous areas is always a challenge. Adopting guidance from other industries will often result in conservative or large hazardous areas and have a significant impact on the amount of mechanical and electrical equipment located within the zones. It requires a balanced approach between the hazardous area classification and the installation of equipment in hazardous areas.
Solution
We examined legacy information, including guidance and studies, to gain sufficient information to develop a consistent and pragmatic approach to Hazardous Area Classification for our client’s sites.
We conducted site surveys in conjunction with a client specialist to complete specific Hazardous Area Classifications for each site whilst also gaining knowledge of generic requirements that would need to be addressed at future sites. The surveys enabled us to add value to the project by identifying good practices that could be adopted across the fleet of installations. We also identified diesel and battery charging facilities and provided a proportionate classification.
The resulting classifications provided an approach and will assist the inspection team in their projections.
At a glance
Client
Confidential
Location
UK
Services
DSEAR, hazardous area classification, risk management
The project featured in this article was undertaken by RPS, A Tetra Tech Company and originally published on RPSgroup.com. In March 2026 RPS rebranded to Tetra Tech.