R. Meyer J. Köhler A. Homburg Explosives

Fumes
Table 15.
Fume Class Toxic Gases Toxic Gases
ft 3 /lb l/kg
1 less than 0.16 10
2 0.16–0.33 10–21
3 0.33–0.67 21– 42
144
In the European Community the Standard EN 13631-16 “Detection
and Measurement of toxic gases” specifies a method for quantification
of nitrogen oxides and carbon oxides produced by the detonation of
explosives for use in underground works.
The test is carried out in a blast chamber with a minimum volume of
15 m3 , which shall be designed to withstand the forces during the
detonation of high explosives and to prevent a significant loss of
blasting fumes. The chamber is equipped with a thick walled steel tube
(inner diameter of 150 mm, length of 1400 mm) and with an effective
mixing system to ensure a homogeneous gas phase. The chamber
has ports for gas sampling and for measuring the ambient temperature
and pressure.Cartridged explosives and bulk explosives filled
in glass or aluminium tubes can be used. The explosive charge shall
have the minimum diameter for application and a length of 700 mm or
at least seven times the diameter. The explosive mass-to-chamber
volume ratio shall be between 30 g/m3 and 50 g/m3 .
The explosive charge is placed centrally in the bore of the steel tube
and fired there. The initiation is done as recommended by the manufacturer.
If booster charges are necessary their proportion in the fumes
produced has to be considered in the calculation.
For sampling a gas extraction system has to be used, which prevents
the condensation of water vapour and the subsequent dissolving of
nitrous oxides.
The quantity of CO, CO2, NO and NO2 is measured simultaneously
and continuously over a period 20 min. The concentration of CO and
CO2 are constant over the entire measuring period, provided the blast
chamber is sufficiently gas tight. Since NO and NO2 give subsequent
secondary reactions, measured concentration is extrapolated to obtain
the initial concentration. From the initial concentrations so determined,
the volume of the chamber and the amount of the explosive fired, the
amount of each toxic gas is calculated in litres per kilogram of explosive
(at standard temperature and pressure.) The test is performed
three times.
Limits for the toxic gases are not required in the European Standard.
However, the measured amounts can be used by national authorities
for regulations of the underground use of explosives.