17.2.1 The
equipment is to consist of a permanently fixed installation and at
least two sets of portable equipment suitable for the process or products
involved.
17.2.2 The
position and number of fixed sampling points should be determined
with due regard to the density of the gases and/or vapours of the
substances processed or produced, and the dilution resulting from
compartment ventilation. In each case, a sufficient number of sampling
points is to be provided to give efficient selective sequential sampling
to maintain a safe environment.
17.2.3 Unmanned
or closed compartments, such as cofferdams, etc. associated with plant
processing or producing flammable or toxic substances, are to have
permanently installed sampling points suitable for use with portable
detection equipment to be used before entry of the spaces by personnel
and thereafter continuously while occupied by them.
17.2.4 Arrangements
of the sampling point pipe runs are to be such that there is no possibility
of hazardous gases and/or vapours entering a safe space. Common sampling
lines to the detection equipment are not to be fitted.
17.2.5 The
permanently installed gas detection system is to give audible and
visible alarm, both in the control station and within the compartment,
during hazardous conditions.
17.2.6 Except
where continuous sampling is required (i.e. as in Pt 7, Ch 2, 7.2 Safety precautions 7.2.5), the gas detection equipment
should be capable of sampling and analysing from each sampling point
at agreed intervals, which are in no case to exceed 30 minutes.
17.2.7 The
gas detection equipment is to be designed so that it may be readily
and regularly tested and calibrated. Suitable equipment and span gas
is to be provided for this purpose. In addition, regular checking
procedures with portable equipment are to be provided, particularly
for closed or unmanned spaces during process plant operation.
17.2.8 Where
equipment for detecting the specific flammable, toxic or asphyxiate
substances which may be present in process plant spaces cannot be
provided, full details are to be submitted, including personnel protection
requirements and arrangements for decontaminating such spaces if necessary.