Series editors' preface - Wood Tools

(a)
(b)
Figure 9.11 Examples of appropriately labelled
solvents
Conservation preliminaries 425
describe the dangers of the chemicals in more
detail, e.g. ‘May cause cancer’ or ‘Toxic by
inhalation’. Risk phrases can be found in
Croners Substances Guide. Each risk phrase
has a number, e.g. ‘27 Harmful by Inhalation’,
with higher numbers generally indicating
higher risk. Risk phrase numbers are also given
in some suppliers catalogues.
Safety phrases are standard phrases, also set
out in the CHIP Regulations, that tell the user
what to do or what not to do with the chemical,
e.g. ‘Keep away from children’ or ‘ Do not
empty into drains’. Safety phrases are also
numbered and can be obtained from the same
sources as risk phrases.
The Maximum Exposure Limit (MEL) is one
of two types of Occupational Exposure Limit
(OEL), the other being the Occupational
Exposure Standard (OES). The MEL is the maximum
concentration, measured in mg/m 3 or
parts per million (ppm), of an airborne substance,
averaged over a reference period (LTEL
8 hours, STEL 10 minutes) to which employees
may be exposed through inhalation under any
circumstances. CoSHH legislation requires
employers and managers to keep exposure to
MEL assigned substances to as low a level as
reasonably practicable. It is an offence to
exceed an MEL. If a substance has an MEL
(substances with MELs are listed in EH40
Occupational Exposure Limits) then work must
be contained to the lowest level possible of
that substance. It is a criminal offence to go
over the limit.
The OES is the concentration of an airborne
substance at which, according to current
knowledge, there is no evidence that there is a
risk to health if exposed to that level of concentration
day after day. Employers and managers
are required to keep levels of exposure
to such substances at, or below, the limit set.
Substances with an OES are listed in EH40
Occupational Exposure Limits.
Both OES and MEL may be quoted as a longterm
exposure limit or as short-term exposure
limit. Long-term exposure limit (LTEL 8 hour
time-weighted average) is the level of exposure
averaged out over the typical working period
of 8 hours. Short-term exposure limit (STEL,
e.g. 10 minute reference period) is the level of
exposure in any 10 minute reference period.
Short term exposure limits are listed for those
substances for which there is evidence of a risk