Dangerous Substances Explosive Atmosphere - DSEAR

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             Dangerous Substances Explosive
Outlined below are the DSEAR legal foundations, rules and regulations, they also cover why water is the most
valuable of human commodities, fires and explosions, technical safety parameters, the fire danger triangle, the
danger potentials and measures for danger prevention.

DSEAR legal foundations, rules and regulations
The following are the DSEAR legal foundations, rules and regulations for the UK and shows the importance of
DSEAR compliance in the workplace:

•   Management of Health and Safety at Work Regulation 1999
•   Workplace Health Safety and Welfare Regulation 1992
•   Personal Protective Equipment at Work regulation 1992
•   COSHH Control of Substances Hazardous to Health 2002
•   DSEAR Dangerous Substances Explosive Atmosphere Regulation 2002
•   Corporate Manslaughter Act 2008 + Health and Safety Offences Act 2008
•   Water Resources Act -1991 Part 5 - Control of Pollution of Water

DSEAR applies when there is work being carried out by an employer (or self employed person) and 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 energetic events.

The activities covered by DSEAR include storage of petrol as a fuel for cars, boats or horticultural machinery; the
use of flammable gases, such as acetylene for welding; the handling and storage of waste dusts in a range of
manufacturing industries; handling and storage of flammable wastes, i.e. fuel oils; welding or hot work on tanks /
drums that have contained flammable material; the use of flammable solvents in laboratories; and transporting
flammable substances in containers around a workplace.

When working in any industry DSEAR places duties on the employers (and the self-employed, who are
considered employers for the purposes of the Regulations) to assess and eliminate or reduce risks from
dangerous substances and to comply with DSEAR means the employer needs to assess any risks, thereby
preventing or controlling risks using :-

   Control measures,
   Preparing emergency plans and procedures,
   Identifying places where explosive atmospheres may occur („ATEX‟ requirements) and providing information,
    Instruction and training for employees.

Water – The most valuable of human commodities
Water pollution is ever-increasing as world population grows, putting a strain on our existing purifying resources.
Examples of water pollution could be seen in Switzerland in 1986 with the Sandoz fire on 1 November with
devastating ecological consequences. 200 Km of total pollution swept from Switzerland through to Germany and
Holland to the North Sea, causing 20 Km of dead fish in the Rhine.

This one event sparked the birth and foundation of the Denios Group.

Fresh water / Drinking water

Water is a valuable commodity that must be used sparingly and carefully. The human body is about 60% water
in adult males and 55% water in adult females.

Small amounts of harmful substances e.g. oil, are sufficient to pollute
large quantities of water and one million tons of oil flows each year into
the oceans. Approximately 100,000 tons of oil is washed into the ocean
from Tanker disasters and approximately 400,000 tons of oil is washed
into the ocean during oil production, so where does the remainder come

This oil is from all around us! From a dripping oil sump (because a gasket
has perished), to a car being washed and drop by drop oil flows from the
street into the groundwater. When filling a tank two or three drops spill
onto the ground or when filling a lawn mower, chainsaw or other tools, a
few drops drip onto the lawn. Worldwide this means enormous quantities
of drops are lost every year… and that amounts to 500,000 tons of oil!

The statistics are that one drop of oil pollutes 1,000 litres of water and
1 litre of oil makes 1 million litres of water unusable as drinking water.            Photography: Drop of oil in water

Polluting the water is an offence according to Water Resources Act 1991 Section 85.
If storage is not in accordance with the regulations insurance cover may be invalidated!

The Environmental Pollution Prevention Guidelines – PPG26 – details a basic sump volume calculation, which is
applicable to chemical storage. Bunds and Sumps must hold 110% of the contents of the largest container or
25% of the total volume stored. The one exception to this rule is where Agri-Chemicals are in use, Sumps must
hold 185% of the largest container.

Fires & Explosions

The average cost for fire damage is £100,000 and there are 200 primary fires per year. The insolvency quote is

So why do fires start?

A liquid that produces vapour in such quantities that, when mixed with air, it combines to form a flammable
atmosphere is defined a „Flammable Liquid‟.

There are 3 flammable categories:
A) R10 - Flammable Liquids
    Liquids with a flashpoint equal to or greater than 21 degrees C and less than or equal to 55 degrees C,
    which support combustion when tested at 55 degrees C.
B) (F) R11, R15, R17 - Highly Flammable Liquids
    Liquids with a flashpoint lower than 21 degrees C but are not classified as extremely flammable.
C) (F+) R12 - Extremely Flammable Liquids
    Liquids with a flashpoint lower than 0 degrees C and with a boiling point lower than or equal to 35 degrees

The Flashpoint is the lowest temperature at which vapours are given off in such quantities that when mixed with
air, combine to form a flammable mixture,

i.e.                      Diesel                                  55 ºC
                          Alcohol                                 12 ºC
                          95 Octane Petrol                      - 40 ºC
                          Petroleum Ether 40-60º                - 30 ºC    (differs with mix)
                          Turpentine Substitute                   38 ºC    (bottle not marked flammable)

If the surface temperature of a flammable substance passes the Auto ignition temperature, then the vapour
pressure of the flammable substance is so high that the arising gas-air mixture self-ignites without external
                                                                              Flash Point
                          Diesel                                 260 ºC          55 ºC
                          Alcohol                                420 ºC          12 ºC
                          95 Octane Petrol                       450 ºC        - 40 ºC
                          Petroleum Ether                        250 ºC        - 30 ºC
                          Turpentine Substitute                  210 ºC          38 ºC

The Fire Danger Triangle
                                                                      Fuel                    Ignition
The elements making up the fire danger
triangle are Fuel, an Ignition source and Oxygen.

The Ignition source could be a hot surface, a
naked open flame, static-electrical discharge or a
mechanical or electrical spark. An exothermic
reaction can also be an ignition source.
The severity of danger is highly dependant on the
relative proportion of fuel to oxygen mix when combined
with an ignition source.

The Danger Potentials

The most commonly used industrial gases are heavier than air, i.e. they possess a density greater than
1.28g/litre at 25°C and 1 bar pressure. The gases therefore sink to the deepest accessible level (cellar,
basements, etc.) and slowly displace the normal, breathable air mixture.

If these gases are odourless, such as CO2, or are only detectable by smell in high concentrations, such as
ammonia, there is a very real danger of choking to death. With ammonia there is an additional danger of
explosion. (Lower explosion limit: 15%, Upper explosion limit 28%).

The recommendation would be to use built-in or portable gas warning detectors.

Gases from flammable liquids!

In this scenario a solvent is being used for cleaning on the
upper floor and on the ground floor welding is taking place.
Both employees consider that they have correctly evaluated
their own Risk Assessment.

The ignition source and the solvent are separated in different rooms
and responsibility i.e. the employee working with e.g. a welding
torch, knows nothing about the cleaning action of his colleague
in the area above and vice versa.

   Solvents           Ignition Sources              Evaluation
   above              yes                           no                 not critical
   below              no                            yes                not critical
   TOTAL              YES                           YES                CRITICAL

Communication between staff and more information given would be recommended.

Heavy Gases, Heavier than Air

Risk assessments need to be carried out on all activities within
the workplace, including smoking in doorways and an
awareness of other activities close by is also necessary.

The potential danger when we increase the surface area of a
chemical and introduce an ignition source is apparent in the
following situation.

A lubricant with an ignition point between 21°C and 55°C is
used with an aerosol and thus its surface area is increased.
If this sprayed liquid comes into contact with an ignition
source, it begins to burn even at room temperature.

You should always switch off ignition sources when using combustible liquids.

                                       Here a combustible liquid with an ignition point over 55°C is left on a
                                       windowsill for several hours exposed to direct sunlight and if these heated
                                       liquids then come into contact with an ignition source, they begin to burn
                                       even at normal room temperature.

                                       All combustible liquids should be stored responsibly.

Hot surfaces

Combustible solids, paste-like liquids, gaseous yet mostly organic substances often come into contact with a hot
surface (e.g. engines, transmission mounting). Atex Rated equipment must be used in all potentially hazardous
Zoned areas.

If the surface temperature is greater than the ignition temperature of the combustible substance, there is a
danger that it will self-ignite without external influence.

All combustible substances should be kept away from hot surfaces.

Increase in surface area

Steel wool, empty batteries and other objects are often disposed of in the same waste container.

The voltage/energy left in an "empty" battery is sufficient to ignite the fine steel wool with an electric spark, or the
collision of two objects creates a mechanical spark that is sufficient to ignite the fine steel wool.

Waste separation and correct disposal is recommended at all times.

The Danger Triangle

A Danger Triangle will exist dependant                                    Combu                    Ignitio
on the Relative Proportion of Fuel to                                      stible                     n
Oxygen.                                                                   substa Oxygen            source
An Oxygen enriched environment acts
as a fire-propagating agent. It is common
for Oxygen to leak out from defective valves
on an Oxygen flask.
A usual combustion process conceals a high
danger potential, as the Oxygen is a fire-propagating gas.                               n
The more Oxygen, the more intense the combustion process:
Our atmosphere contains 21% Oxygen and with an increase
of just 3% to 24% proportion of Oxygen, then the speed of
burn-up doubles. Therefore an appropriate, responsible
handling of Oxygen should always be maintained in the workplace.

So when you have Oxygen present in the atmosphere, you can easily provide various sources of ignition and
these include hot surfaces; naked open flame; static-electrical discharge; mechanical or electrical spark.

The big question is how much fuel do you need to make an explosive atmosphere?

If you have lean mixture of 1 or 2 eye drops of fuel in a 500 ml bottle then the risk of explosion is slight, whereas
when the quantity and ratio are just right, then only 5 eye drops of flammable liquid can produce an explosive
atmosphere in a 500 ml bottle.

So if you add 30 eye drops of fuel to a 500 ml bottle giving a rich mixture there will be no danger of an explosion
but there would be a big danger of fire.

                              Upper and lower explosion limit in % by volume

                      Lower explosion limit 15%        Ammonia         Upper explosion limit 28%

                                                       20%            40%            60%           80%

                   Lean Mixture         Perfect Explosive Atmosphere Mixture             Rich Mixture

The facts are:
5 drops combustible liquid evaporate to 500 ml ignitable mixture
1 jigger (20 ml) of combustible liquid evaporates to a 205 litre drum of ignitable mixture
1 litre combustible liquid evaporates to 50 x 205 litre drums = 10,000 litre ignitable mixture

Empty Drums

Relating to work practice, supposedly empty drums should be rinsed out with water and then taken to the waste
disposal, but empty vessels that are not completely cleaned of combustible liquids, as a rule, contain explosive
atmospheres. Therefore there should be no welding, grinding, or use of cut-off wheels.

Combustible Dust

What happens when Combustible Dust comes into contact with a heat source e.g. Coal, Flour, Wood, Grain,
Sugar, certain Metals and Synthetic Organic Chemicals. If this dust is disturbed and comes into contact with an
ignition source there is the danger of a dust explosion. (From a particle size of <0.5 mm combustible dust there
is a risk of a devastating explosion.)

The recommendation is to regularly remove dust deposits and always use explosion-proof production facilities.

                Explosion Protection documentation
                                        RISK ASSESSMENT

In DSEAR, an explosive atmosphere is defined as a mixture of dangerous substances with air, under
atmospheric conditions, in the form of gases, vapours, mist or dust in which, after ignition has occurred,
combustion spreads to the entire unburned mixture.

Atmospheric conditions are commonly referred to as ambient temperatures and pressures, which means,
temperatures of –20°C to 40°C and pressures of 0.8 to 1.1 bar.

In the course of a risk assessment, any explosive atmosphere above a quantity of 10 Cu litres, should be
considered highly dangerous. Independent of the number of persons employed, an explosion protection
document should be issued to all persons and in-addition, all persons should be made fully aware of the
potential of Explosion and Danger.

We are the main cause for explosions and incidents at work
The main causes for explosions and incidents in work are: instructions which are incorrectly used, followed or
incomplete; insufficient instruction and/or supervision; Insufficient and/or ambiguous responsibility/task and un-
authorised delegation.

Measures for Danger Prevention – External and Internal Bulk Storage

There are a number of cabinets and storage solutions to prevent fire and explosions in the workplace and these
include: walk-in – 90 Minute Fire Rated Storage; walk-in – External Flammable Storage; Drum External
Flammable Storage; IBC External Flammable Storage and Insulated Fire Resistant Storage.

Within this range of storage solutions, systems can be added to increase the prevention of fire and explosions,
including Heater systems; Cooling systems; Air-conditioning systems; Fume and air extraction systems; Heat
detection and fire alarm systems; Control systems; Dispensing systems and Remote station systems.

Measures for Danger Prevention – Internal Small container Storage
For internal flammable storage for single-skin cabinets, the old 30 minute fire protection standard BS476 would
actually only achieve a 2-3 minute fire protection. This old BS standard was used for daily use storage only for a
maximum of 50 litres, for highly or extremely flammable materials.

HSE Key Facts

The new HSE position “Limits of Storage Quantities” states that, “it is recommended that the maximum
quantities that may be stored internally is no more than 50 litres for extremely or highly flammable liquids. No
more than 250 litres for flammable liquids with a higher flashpoint of up to 55°C. (DSEAR ACoP L135, paragraph
40 refers)”

These quantities are intended to be viewed as recommended maxima representing good industry safe practice,
rather than be taken as absolute limits.

The new HSE position “Storage Cupboards”, paragraphs 94, 96 and 104 in the DSEAR ACoP L136 details the
performance requirements for fire resisting cupboards and bins. It is important to recognise that these do not
specify an absolute test or standard for the cupboard or bin itself, rather they relate to nominal construction

Materials used to form the sides, top, bottom, door(s) and lids are capable of providing the required fire
resistance (30 minutes integrity) and reaction to fire. Joints between the sides, top and bottom of cupboards and
bins should be free from openings or gaps, to prevent the passage of Hot Flame or Gases. The lid or doors
should be close fitting against the frame of the bin/cupboard, supports and fastenings should be of a material
with a melting point greater than 750°C. WARNING – ALUMINIUM MELTS AT 690°C.

These criteria represent the minimum performance requirements for compliance with
the current legislation!

ACoP 136 paragraph 104 – Joints between the sides, top and bottom of cupboards and bins should be free from
openings or gaps. Therefore, It is reasonable to conclude that the cabinet should not allow the passage of Hot
Flame or Gases.

Internal Flammable Storage
EN-BS 14470 Fire Cabinets with 90 minutes fire protection

The actual protection using EN-BS 14470 is 30-90 minutes and up to 250 litres can be stored in any one cabinet.
The cabinet includes standard design features, including auto-close vents, auto-close and lock doors and fusible

Extinguish – but do it right

The potential danger with fire in the workplace is the lack of knowledge about combustible substances, which
results in an unsuitable extinguishing agent being chosen. In the worst-case scenario this can even make the
effects of the fire considerably worse.

When a full risk analysis has been done, then the correct extinguishing agent can be correctly positioned and be
readily to hand with full instructions.

                 Extinguish – The importance of getting it right

                                                        Fire Classes
      Solvents                    A               B               C              D               F
                                Solids         Liquids          Gases          Metals        Cooking fat
                                  +             x (1)             -             x   (2)         x   (3)

                                  +              +                -             x   (2)         x   (3)

      BC Powder
                                  -              +                +               -              -
      ABC Powder
                                  +              +                +               -              -
      Metal fire
                                  -                -              -               +              -
      Fat fire
                                  -               +               -               -              -
      extinguishing agent         +                -              -               -              +
      + = suitable
      - = unsuitable
      x = unsuitable: Use conceals particular dangers
      (1) Danger of fire spreading
      (2) Danger of a violent, in certain circumstances, explosive reaction
      (3) Danger of fat explosion
To summarise the measures for Danger Prevention
Technical solutions, laws, directives and regulations only help to avoid the dangers, remember, the most
important thing is to ensure that it is the personal responsibility of every single employee to be vigilant when
storing and handling Hazardous Substances and Materials. In addition, treat this subject with contempt and you
can be ensured of just one thing DISASTER is just around the corner.