DSEAR Assessment: How to Do One Yourself

Where to Start

A DSEAR risk assessment answers one question: if the flammable or explosive substances in your workplace were released or ignited, what would happen, and what are you doing about it?

The structure is not something you have to invent. Regulation 5(2) of the Dangerous Substances and Explosive Atmospheres Regulations 2002 is itself a ten-point checklist — it lists exactly what the assessment must consider. Work through those ten points for each dangerous substance or activity and you have done the assessment.

Most of the pages you will find on this are written by consultancies, and they are written from the point where you hire one. That is genuinely the right answer for hazardous-area classification in a complex plant. It is not the right answer for a workshop with a flammables cabinet and a parts washer, where an owner who knows the site can do most of this properly and then buy help for the part that actually needs it. This guide is written for that second case, and it says clearly where the line is.

If you are not yet sure whether DSEAR applies to you at all, start with DSEAR and COSHH: which applies — the two regimes split along the CLP hazard classes, and it is worth getting that straight first.

Step 1: List Your Dangerous Substances

Everything else depends on this list being right.

Go through your existing chemical register and mark anything that meets the DSEAR regulation 2 definition — anything classified in a physical hazard class under CLP, anything that creates risk because of its physico-chemical properties and how you use it, and any dust "which can form an explosive mixture with air or an explosive atmosphere".

In practice that means looking for:

Flame, flame-over-circle (oxidising) and exploding-bomb pictograms on the label
A flash point in section 9 of the safety data sheet — anything below about 60°C deserves attention, and anything below 23°C much more so
Compressed and liquefied gases, including welding and catering cylinders
Combustible dusts generated by your processes — wood, flour, sugar, grain, metal, plastics. These never arrive in a labelled container, which is exactly why they get missed

Record the quantity you hold of each and where it is held. You will need both in step 3, and the quantity figure does more work than people expect.

Step 2: Work Through Regulation 5(2)

This is the assessment. Regulation 5(2) requires it to include consideration of:

Reg 5(2)	What it means on your site
(a) the hazardous properties of the substance	Flash point, explosive limits, autoignition temperature, incompatibilities — all from the SDS
(b) information on safety provided by the supplier, including information contained in any relevant safety data sheet	The SDS itself, plus anything on the label or in supplier guidance
(c)(i) the work processes and substances used and their possible interactions	Decanting, spraying, mixing, heating, cleaning — and what could meet what
(c)(ii) the amount of the substance involved	Bulk store vs working stock. This drives the answer more than anything else
(c)(iii) where the work will involve more than one dangerous substance, the risk presented by such substances in combination	Two individually manageable substances stored together may not be
(c)(iv) the arrangements for the safe handling, storage and transport of dangerous substances and of waste containing dangerous substances	Including the waste — solvent-soaked rags are a dangerous substance
(d) activities, such as maintenance, where there is the potential for a high level of risk	Tank cleaning, filter changes, hot work, anything that opens a closed system
(e) the effect of measures which have been or will be taken pursuant to these Regulations	Credit for the controls you already have
(f) the likelihood that an explosive atmosphere will occur and its persistence	The zoning question, in plain terms
(g) the likelihood that ignition sources, including electrostatic discharges, will be present and become active and effective	Not just naked flames — static, hot surfaces, electrical equipment, vehicles
(h) the scale of the anticipated effects of a fire or an explosion	Who and what is nearby
(i) any places which are or can be connected via openings to places in which explosive atmospheres may occur	Drains, ducts, gaps under doors, inspection pits
(j) such additional safety information as the employer may need in order to complete the risk assessment	Anything else you need to finish the job

Two of these are worth dwelling on.

Paragraph (i) is the one that gets missed. Most flammable liquid vapours — solvents, thinners, fuels — are heavier than air. HSE's HSG51, Storage of flammable liquids in containers (third edition, 2015) puts it plainly at paragraph 41: "Flammable liquid vapours are heavier than air and will unless dispersed tend to accumulate at lower areas." Those will find a drain, a duct or the gap under a roller shutter and travel to somewhere you never assessed — a boiler room, a pit, a neighbouring unit.

It is not a universal rule, and assuming it is will lose you the other half of the hazard. Hydrogen is the standard counter-case — flammable, and buoyant rather than dense. HSE's INDG139, Using electric storage batteries safely is explicit at paragraph 43: "The buoyancy of hydrogen causes it to rise from the battery and accumulate against ceilings or bulkheads." So in a battery-charging bay the roof void and the high points are where the gas collects, and those are the places your walk-round has to reach — not just the floor. The ventilation that follows from it is not high-level vents on their own, though. The same paragraph specifies a through-flow arrangement: charging areas and battery compartments or enclosures "should be equipped with appropriate air vents, ie inlets at low level and outlets at high level", and "these should be located in two opposing exterior walls or in a door and an opposing exterior wall". Walk the route in both directions.

Paragraph (g) is broader than "no smoking". Electrostatic discharge is named explicitly in the text. So is the more general category of ignition sources: hot surfaces, mechanical sparks, electrical equipment not rated for the location, vehicle engines, mobile phones in the wrong place.

Step 3: Eliminate or Reduce, in the Order the Regulation Sets

Regulation 6(1) requires risk to be "either eliminated or reduced so far as is reasonably practicable", and regulation 6(2) puts substitution first — replacing the substance or process with one that removes or reduces the risk. Water-based rather than solvent-based; higher flash point rather than lower.

Where you cannot eliminate, regulation 6(4) gives seven measures "in order of priority":

"(a) the reduction of the quantity of dangerous substances to a minimum; (b) the avoidance or minimising of the release of a dangerous substance; (c) the control of the release of a dangerous substance at source; (d) the prevention of the formation of an explosive atmosphere, including the application of appropriate ventilation; (e) ensuring that any release of a dangerous substance which may give rise to risk is suitably collected, safely contained, removed to a safe place, or otherwise rendered safe, as appropriate; (f) the avoidance of— (i) ignition sources including electrostatic discharges; and (ii) adverse conditions which could cause dangerous substances to give rise to harmful physical effects; and (g) the segregation of incompatible dangerous substances."

Read the order. Cutting the quantity you hold is first. Avoiding ignition sources is sixth. Most workplaces start at (f) because it is visible and cheap — signs, non-sparking tools, a no-smoking policy — and never revisit (a), which is usually the single most effective thing available and often costs nothing but a change to ordering habits.

If you hold 200 litres of a solvent because that is the drum size the supplier sells, and your actual monthly use is 15 litres, the assessment has just told you something concrete.

Regulation 6(5) then covers mitigation — reducing the number of employees exposed, preventing propagation of fire or explosion, pressure relief, suppression equipment, plant built to withstand pressure, and PPE. And regulation 6(6) carries the storage duty: "The employer shall arrange for the safe handling, storage and transport of dangerous substances and waste containing dangerous substances." The general safety measures in Schedule 1, applied under regulation 6(8), cover the workplace and work-process side — design, construction, maintenance, equipment that stays safe on power failure, manual override by competent employees.

This is the same working-down-the-list discipline as the COSHH hierarchy of control, and it earns its keep the same way: what matters is being able to show why you stopped where you did.

Step 4: Decide Whether You Need Zoning

Regulation 7(1) requires employers to classify places where an explosive atmosphere may occur into hazardous or non-hazardous, and to classify the hazardous ones into zones under Schedule 2.

The trigger is narrower than the fear of it. Schedule 2 paragraph 1 sets the test:

"A place in which an explosive atmosphere may occur in such quantities as to require special precautions to protect the health and safety of the workers concerned is deemed to be hazardous within the meaning of these Regulations. A place in which an explosive atmosphere is not expected to occur in such quantities as to require special precautions is deemed to be non-hazardous within the meaning of these Regulations."

So the question is not "do we have anything flammable?" — it is "can enough of it get into the air, in this place, to need special precautions?" A cabinet holding a few litres in closed containers, opened occasionally in a ventilated workshop, usually will not. Open decanting of solvent in a small room, a spray booth, a dust extraction system, or a place where a gas cylinder could leak into a confined space are a different matter.

Where places are hazardous, Schedule 2 paragraph 2 classifies them by how often and how long an explosive atmosphere is present:

Zone	Applies to	Definition (Schedule 2)
0	Gas, vapour, mist	"present continuously or for long periods or frequently"
1	Gas, vapour, mist	"likely to occur in normal operation occasionally"
2	Gas, vapour, mist	"not likely to occur in normal operation but, if it does occur, will persist for a short period only"
20	Combustible dust cloud	"present continuously, or for long periods or frequently"
21	Combustible dust cloud	"likely to occur in normal operation occasionally"
22	Combustible dust cloud	"not likely to occur in normal operation but, if it does occur, will persist for a short period only"

Once a place is zoned, Schedule 3 sets requirements for the equipment and protective systems used in it, and Schedule 4 covers the warning signs at entry points. Regulation 7(5) also requires work clothing that does not generate electrostatic discharges.

Where to Stop and Get Help

Here is the honest boundary, and it is drawn by the regulation rather than by a sales page.

Regulation 7(4) requires that, before a workplace containing hazardous places is used for the first time, overall explosion safety is verified by "a person who is competent in the field of explosion protection as a result of his experience or any professional training or both."

So: if your assessment concludes that no place needs classifying, you can reasonably complete and record that yourself — with the reasoning written down, because "we considered it and concluded no zone applies" is a defensible position and silence is not. If it concludes that a place does need classifying, the regulation itself puts a competent person in the loop. Selecting equipment categories for a zone, and verifying overall explosion safety, is specialist work. Getting that wrong is not the kind of mistake you find out about gradually.

The useful thing is that steps 1 to 3 — the substance list, the regulation 5(2) walk-through, the quantity reduction — are work you do either way, and doing them first makes any specialist engagement shorter and cheaper, because you arrive with the inventory and the process description already written.

Step 5: Record It, and the Rest That Follows

Recording. Regulation 5(4) requires an employer with five or more employees to record the significant findings — including the measures taken, information showing the workplace and work processes are designed, operated and maintained with due regard for safety, and, where an explosive atmosphere may occur, the zones classified, the equipment required, the regulation 7(4) verification, and the aim of any co-ordination. Below five employees the assessment is still required; only the recording duty is lifted. In practice, write it down anyway — it is how you show it happened.

Before the work starts, not after. Regulation 5(5): "No new work activity involving a dangerous substance shall commence unless— (a) an assessment has been made; and (b) the measures required by these Regulations have been implemented."

Review. Regulation 5(3) requires the assessment to be "reviewed by the employer regularly so as to keep it up to date", and particularly where there is reason to suspect it is no longer valid or the workplace, processes or organisation of the work have significantly changed. That is nearly the same trigger as the COSHH assessment review, so put both on one cycle rather than two.

The duties that sit alongside the assessment. Regulation 8 requires emergency procedures, first-aid facilities and safety drills tested at regular intervals, plus warning and communication systems. Regulation 9 requires information, instruction and training on the substances and the significant findings — parallel to COSHH regulation 12, and satisfiable in the same session. Regulation 10 requires containers and pipes to be clearly identifiable where they are not already marked under the legislation in Schedule 5. And regulation 11 puts the co-ordination duty on the employer responsible for a shared workplace where an explosive atmosphere may occur — worth knowing if you are in a multi-unit industrial estate.

Quick Checklist

One List, Two Assessments

The practical difficulty with running DSEAR alongside COSHH is not the assessment — it is keeping one accurate substance list behind both, so a new product gets looked at for flammability as well as for health, and so a review date means something for both documents.

COSHHmate is being built around that register: each substance carries its classification once, assessments hang off it, and a change to a substance surfaces everything that depends on it. Pricing will be a flat monthly fee with no per-user charges. If your two regimes currently live in two folders, join the waitlist.

Sources

This is general guidance based on the published text of the Dangerous Substances and Explosive Atmospheres Regulations 2002, which extend to England, Wales and Scotland; Northern Ireland has its own equivalent instrument enforced by HSENI. Hazardous-area classification and the selection of equipment for a zone are specialist work — regulation 7(4) requires verification by a person competent in explosion protection, and this guide is not a substitute for that. Not legal advice.