CO₂ POISONING SYMPTOMS - [...]
CO₂ level - about 600ppm which
is typical of indoor air and is
an acceptable and safe level.

At 1% concentration of carbon dioxide
CO₂ (10,000 parts per million or ppm)
and under continuous exposure at that
level, such as in an auditorium filled
with occupants and poor fresh air
ventilation, some occupants are likely
to feel drowsy.

The concentration of carbon dioxide
must be over about 2% (20,000 ppm)
before most people are aware of its
presence unless the odor of an
associated material (auto exhaust or
fermenting yeast, for instance) is
present at lower concentrations.

Above 2%, carbon dioxide may cause
a feeling of heaviness in the chest
and/or more frequent and
deeper respirations.

If exposure continues at that level
for several hours, minimal "acidosis"
(an acid condition of the blood) may
occur but more frequently is absent.

Breathing rate doubles at 3% CO₂ and
is four times the normal rate at 5% CO₂.

Toxic levels of carbon dioxide: at levels
above 5%, concentration CO₂ is directly
toxic. [At lower levels we may be seeing
effects of a reduction in the relative
amount of oxygen rather than direct
toxicity of CO₂.]

Symptoms of high or prolonged exposure
to carbon dioxide include headache,
increased heart rate, dizziness, fatigue,
rapid breathing, visual and hearing
dysfunctions. Exposure to higher levels
may cause unconsciousness or death within
minutes of exposure.
www.inspect-ny.com/hazmat/CO2gashaz.htm