Gasoline fumes are lighter than air

Appendix 4

Examples of particular hazards caused by gases and vapors in enclosed spaces in wastewater systems

Liquids, gases and vapors can be introduced into enclosed spaces of wastewater systems through impermissible discharges or in accidents or arise as a result of chemical or biological reactions. The presence of these substances can be dangerous. As a rule, these are dangers from:

Lack of oxygen (O2-Defect)

All additionally introduced gases and vapors reduce the oxygen content in the atmosphere of the a. A ..

Concentration of O2 in the air Symptom / effect 
20.9% by volume Concentration in the unpolluted fresh air
<18 vol .-% Harmful to health
<10% by volume Less than 10% by volume of oxygen, consciousness disappears without warning. Brain damage and death follow in minutes if resuscitation cannot be immediate.


Petrol fumes

All vapors from flammable liquids are heavier than air.

Concentration of gasoline vapors in the airSymptom / effect
~ 0.6% by volume Lower explosion limit (LEL)
~ 8 vol .-% Upper explosion limit (UEL)
500 to 1,000 ppmIrritation of the respiratory tract, headache, dizziness, nausea, confusion or even unconsciousness


Carbon dioxide (CO2)

Carbon dioxide is heavier than air.

Concentration of CO2 in the air Symptom / effect 
0.03 vol% Share in the unpolluted fresh air
0.07% by volume City air
0.1-0.3% by volumeHigh values ​​in offices
0.5% by volume / 5,000 ppmOccupational exposure limit (AGW)
approx. 1 - 4% by volumeIrritation of the mucous membranes, acceleration of breathing, rise in blood pressure, excitement, palpitations, headache
approx. 5 - 9% by volumeHeadache, ringing in the ears (tinnitus), palpitations, rise in blood pressure, mental excitement, dizziness, drowsiness
> 9 vol .-%Unconsciousness after 5 - 10 minutes of inhalation
Over 10% by volumeParalysis of the respiratory center, narcosis, death

Methane (CH4)

Methane is lighter than air.

Concentration of CH4 in the air Symptom / effect 
4.4 vol% Lower explosion limit (LEL)
17 vol% Upper explosion limit (UEL)

Hydrogen sulfide (H.2S)

Concentration of H2S in the air in ppmSymptom / effect 
0,003 – 0,02Odor perceptibility
3 – 10clearly unpleasant odor
20 – 30strong rotten egg smell
5 Occupational exposure limit
50 – 100Irritation of the respiratory tract
100 – 200Loss of smell
250 – 500 Toxic pulmonary edema, cyanosis, coughing up blood, pneumonia
500Headache, uncoordinated movements, dizziness, stimulation of breathing, poor memory, loss of consciousness ("knockdown")
500 – 1 000Respiratory arrest, immediate collapse, severe nerve damage, arrhythmic heart activity, death


Digester gas

Digester gas is a gas mixture (e.g. from CH4, CO2, H2S, O2, H2), which can occur in a wide variety of compositions. The density of digester gas is almost only dependent on the ratio CH4/ CO2 certainly. It can be both heavier and lighter than air. In the case of digester gas, the effects of the individual components occur in combination. There is currently no detailed knowledge about the combined effects on humans.