Page 110 - Engineering Rock Mass Classification_ Tunnelling, Foundations and Landslides

unnel

Physiological effect on workers

20.93% O2 At least 20% is required to sustain normal health;
workers become dizzy if concentration drops to 15%;
some workers may die at 12.5%; most will faint at a
concentration of 9%; and death will occur at 6% or
less

78.10% N2 Nitrogen has no ill effect on persons except to dilute
air and decrease O2%

0.03% CO2; CO2 CO2 acts as a respiratory stimulant and may increase
decaying timber effects of other harmful contaminants; at 5% CO2,
breathing is laborious; a concentration of 10% can
s present in diesel
be endured for only a few minutes

el exhaust and CO is absorbed into the blood rather than O2. In time,
very small concentrations will produce symptoms of
poisoning. A concentration slightly greater than
0.01% will cause a headache or possibly nausea.
A concentration of 0.2% is fatal

in rock formations Has no ill effect on persons except to dilute air
bonaceous materials and decrease O2%; it is dangerous because of its
explosive properties; methane is explosive in the
concentration range of 5.5 to 14.8%, being most
explosive at a concentration of 9.5%

in rock formations Extremely poisonous — 0.06% will cause serious
in blast fumes problems in a few minutes

Continued