Environmental Engineering Reference
In-Depth Information
Table 2.11 Hazard concentration of toxic gases in air (mg L
−
1
)
Toxic
gas
Mild poisoning after
several hours
Severe poisoning
after 1 h
Lethal after
0.5
Dying after sev-
eral minutes
1h
-
CO
0.1
-
0.2
1.5
-
1.6
1.6
-
2.3
5
NO
x
0.07
0.2
0.2
0.4
0.4
1.0
1.5
-
-
-
H
2
S
0.01
0.2
0.25
0.4
0.5
1.0
12
-
-
-
SO
2
0.025
0.06
-
0.26
1.0
-
1.05
is still a challenge for all scientists. From the mechanisms, the ideal detonation
reactions only produce CO
2
and N
2
, which are oxidized by oxygen from carbon and
reduced from nitrogen oxides. However, the real detonation reactions are not ideal
redox reactions. In the initial stage of explosion, the reactions are not complete, and
the gas products deviate from expected results. In the detonation products, there are
a lot of toxic gases, mainly carbon monoxide and nitrogen oxides (which include
N
2
O, NO, N
2
O
3
,NO
2
/N
2
O
4
, and N
2
O
5
). All of these gases extremely endanger the
health of human. For example, breathing in CO reduces the ability of blood
transporting oxygen, which leads to severe hypoxia of tissue cells. 0.03 % of CO
concentration in air is not safe. 0.15 % CO will causes suffocation poisoning or
even death. The toxicity of NO
2
is larger than CO. NO
2
with lower concentration
has long-term potential dangers. The toxicity of NO
2
mainly impacts the lungs.
After being breathed in, NO
2
reacts with the moisture in the lungs to produce nitric
acid and nitrous acid, which severely irritate and corrode the lungs tissues until
edema. The toxicity of NO
2
is 6.5 larger than that of CO. If there is not enough
oxygen, or the explosion conditions are not good enough, the products may have
C
m
H
n
,NH
3
, and HCN toxic gases, etc.; explosives with sulfur may produce SO
2
and H
2
S. The toxicity of explosion products are mainly from the below two
components.
(1) Interaction of explosion products and the surrounding media
Some rocks can react with detonation products, and also act as the catalysts of
second reactions. For example, coal can reduce the CO and CO
2
of products. Iron
oxide ore acts as the catalyst of CO oxidization to CO
2
. Sul
de ore reacts with
detonation products to produce sulfur oxide and hydrogen sul
de.
In addition, blasting operation, charge/packing density, charge/packing length,
and stemming blockage of explosion holes impacted the formation of toxic gases to
a certain extent. For industry explosives in blasting, ratio of mixtures, selection of
oxygen balance, processing of explosives, and blasting operation should be taken
into consideration. The hazard concentrations of toxic gases are in Table
2.11
.
(2) Incompleteness of explosion reaction
In the preliminary stage of explosion, the incomplete reactions are very common.
The quenching or freezing impact of balance reaction deviates products from
expected results, and produces a lot toxic gases, especially in composite explosives.
In liquid explosives, addition of sensitizers with high reaction activities (such as
nitroglycerine, hexagon, hydrazine nitrate, hydrazine perchlorate, aromatic explo-
sives, etc.) helps to complete explosive reactions and reduce the production of toxic
