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RISK
ASSESSMENT: USE OF LABORATORY HEATING EQUIPMENT
The equipment considered in this Risk Assessment includes
laboratory ovens, Bunsen burners, heating plates and mantles, steam oil
and sand baths and hot air guns i.e. temperatures up to 800°C. The
use of very high temperatures, furnaces, experimental rigs etc. must be
covered by a separate Risk Assessment.
Hazards
- Personal injury and burns from hot surfaces, liquids, vapours or flames.
- Sources of ignition both from hot surfaces, liquids or flames and
from electrical components.
Risks and who is likely to be injured?
- Contact burns are likely and may range from trivial to severe but
most likely will affect only the user.
- Ignition or explosion is much less likely but may result in widespread
injury to others.
Precautions
Many heating appliances contain electrical elements (see the separate
Risk Assessment "Use of Standard Electrical Equipment"). If
any heating device becomes so worn or damaged that the heating element
is exposed, the device should immediately be taken out of service.
All heating devices (apart from steam baths) must be kept well away from
flammable material.
Ovens
- With the exception of vacuum drying ovens, laboratory ovens rarely
have any means of preventing the discharge of material volatilised within
them. Thus it should be assumed that these substances will escape into
the laboratory atmosphere but may also be present in sufficient concentration
to form explosive mixtures within the oven itself. This hazard may be
reduced by venting the oven to an exhaust system.
- Ovens should not be used to dry any chemical sample that has even
moderate volatility and might pose a hazard because of acute or chronic
toxicity unless the oven is constantly vented to a safe exhaust.
- Glassware rinsed in solvent poses a danger of explosion if dried in
an un-vented oven.
Bunsen Burners
- Bunsen burners are used less and less in laboratories. The naked flame
is liable to set off the fire alarm system if set in the line of sight
of a flame detector. If used, care must be taken to shield the flame
from the detector.
- The naked flame is a particularly hazardous ignition source and must
never be used near open containers of flammable liquid or in environments
where appreciable concentrations of flammable vapour may be present.
- A Bunsen flame may be difficult to see in bright sunlight. Blinds
should be drawn to shade the flame.
Hot Plates, Heating Mantles
The state of the heating element should be checked. If the covering is
broken or worn the equipment must not be used. If water or other liquid
has been spilled onto the element, the equipment must be electrically
checked before use.
Steam, Oil and Sand Baths
- Extreme care must be taken to mount the baths in such a way that they
cannot be overturned or that water cannot fall into an oil or sand bath
causing hazardous splattering. For oil baths, secondary containment
must be used to restrain any possible spills.
- Oil expands in volume when heated:- overfilling should be avoided.
- Material heated in such a bath should be mounted in such a way that
it can be quickly and easily removed from the bath in an emergency.
- Oil must not be overheated so that it smokes or decomposes or is in
danger of ignition.
- Proper labelling should identify the oil and its safe working temperature.
- Attention should be paid to the following:-
- the size and location of the bath,
- operating temperature and temperature control devices,
- the type of oil used,
- available ventilation,
- the method of cooling hot oil,
- storage of oil for reuse,
- proximity of water or chemicals.
- Steam baths present a danger of scalding from hot steam and care must
be taken especially when mounting or removing reaction vessels.
- In all cases, when using such apparatus, proper protective equipment
must be worn i.e. lab. coat, safety glasses and gloves.
Hot Air Guns
- Laboratory hot air guns contain an electrically heated element that
typically glows red hot. Also, the on-off switches and motors are rarely
spark free. For these reasons, hot air guns present as serious an ignition
hazard as a naked flame and must never be used near open containers
of flammable liquid or in environments where appreciable concentrations
of flammable vapour may be present e.g. over glassware rinsed in solvent.
- The air emerging from a heat gun is very hot indeed and is invisible
and so the front end should be treated with all the respect due to a
blow torch.
Training requirement
The use of some of these heating devices i.e. steam baths, Bunsen burners,
hot plates and heating mantles is part of Undergraduate training. In the
remaining cases, training should be given by a competent person.
Level of Risk Remaining
With the proper training, the level of risk is low although constant
vigilance is necessary to avoid injury and possibly serious burns.
Back to Completed Risk Assessment Forms
Adapted
with permission from School of Chemistry, University of Bristol
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