Client Background
The client operates a datacentre supported by battery power for standby continuity. The vented-type batteries were housed in dedicated charging rooms, that are ventilated by fan and/or open louvres, with ventilation running continuously.
Under the Dangerous Substances and Explosive Atmospheres Regulations 2002 (DSEAR), the company is obliged to assess the risk to employees from fire and explosion arising from these operations. Sigma-HSE was commissioned to carry out the assessment.
Client Problem
During charging, batteries evolve hydrogen. Hydrogen is lighter than air, so it rises from the battery under charge and tends to pool in the ceiling. If ventilation with fresh air is not adequate, hydrogen can accumulate to flammable concentrations in the ceiling space. Even where a room’s overall ventilation is sufficient, a small flammable atmosphere may still exist in the immediate vicinity of a battery under charge.
Client Objectives
The client required confirmation of two things: whether the existing ventilation was adequate to dilute the hydrogen released during charging to below flammable concentrations, and whether ATEX-rated equipment would be required.
Sigma-HSE’s assessment found that
Sigma-HSE assessed each battery room’s ventilation against the rate of hydrogen evolution expected, under the conditions which hydrogen production would be the greatest.
- To avoid zoning the room, hydrogen concentration must always remain below 25% of its lower flammable limit.
- All extract points were positioned at high level, reflecting the rooms’ existing dilution ventilation rather than local exhaust capture at each cell, which captures hydrogen before it can accumulate given its tendency to rise and pool at the ceiling.
- Every battery room had fresh air ventilation, either fan-driven or by open louvres. These were confirmed by calculation (International Electrotechnical Commission) to be sufficient to dilute any hydrogen released during charging, comparing expected hydrogen evolution during boost-mode charging against each room’s air change rate.
Recommendations
- Where ventilation is achieved by fan(s), the air flow should be monitored and interlocked with the battery charger, so that charging stops automatically if extraction falls below a specified flow rate. Where ventilation is achieved by open louvres, these should be kept clear of obstructions.
- Equipment and personnel should be earthed in accordance with the battery supplier’s recommendations, as a standing electrical safety practice independent of the zone designation.
- Since the zone designation in the battery rooms was negligible, no ATEX equipment is required.
Outcomes
Because the zone designation across all battery rooms was confirmed as negligible extent, the client was not required to install ATEX-rated equipment, avoiding a retrofit the company had been budgeting for.
In its place, Sigma-HSE issued targeted, low-cost recommendations covering ventilation monitoring, earthing, and confirmation of the negligible-extent finding, giving the client a defensible basis of safety for continued operation.
Book a DSEAR assessment and we’ll guide you to compliance. If your team needs it, we also run DSEAR and ATEX awareness training, so the people working the floor understand the hazards as well as the paperwork does.
