sw” _ 
Marcu 3, 1923] 
NATURE 
293 

Poisoning by Illuminating Gas. 
URING the last few months much attention has 
been given in the public press to the question 
of the poisonous properties of illuminating gas and 
the risk to life which may be incurred if an escape of 
gas should take place in an ordinary dwelling. The 
only constituent of illuminating gas which has serious 
poisonous properties in this connexion is carbon 
monoxide. 
Carbon monoxide has the property of forming a 
dissociable compound with the hemoglobin of the 
blood just as has oxygen, but the affinity of carbon 
monoxide for hemoglobin is about 240 times that of 
oxygen for hemoglobin. The greater the extent to 
which the hemoglobin becomes combined with carbon 
monoxide the less is its capacity to act as a carrier 
of oxygen between the lungs and the tissues of the 
body, and if sufficient of the hemoglobin in the 
blood becomes combined with carbon monoxide the 
normal oxygen supply to the tissues must evidently 
be seriously affected. The effects produced by severe 
carbon monoxide poisoning are, in fact, those of slow 
or rapid asphyxiation. 
If blood is exposed outside the body to air contain- 
ing both oxygen and carbon monoxide the partition 
of the hemoglobin between the two gases follows the 
laws of mass aetion, being determined by the relative 
partial pressure of the gases, allowance being made 
for the difference in their affinities. The air in the 
lungs with which the blood undergoes gaseous inter- 
change contains in man about 14 per cent. of oxygen 
when he is breathing ordinary air. If human blood 
is saturated in vitro at body temperature with an 
atmosphere containing 14 per cent. of oxygen and 34, 
of this proportion of carbon monoxide, i.e. 0-058 per 
cent., the hemoglobin will finally become equally 
divided between the two gases, or 50 per cent. saturated 
with carbon monoxide and 50 per cent. with oxygen. 
If the concentration of oxygen is kept constant and 
that of carbon monoxide is varied the degree to which 
the hemoglobin will become: saturated with carbon 
monoxide is as follows : 
IN THE PRESENCE OF I4 PER CENT. OF OXYGEN. 
, Approximate final percentage 
Percentage of 7 Sane 
; saturation of hemoglobin with 
carbon monoxide. carbon monoxide. 
O°015 20 
0°03 33 
0°06 50° 
o'r2 67 
o'l7 ree 
0°23 80 
If a person is exposed to ordinary air containing 
carbon monoxide the hemoglobin in his blood will 
gradually become saturated with carbon monoxide 
just as in the experiments in vitro, and the degree of 
saturation will finally attain a steady value dependent 
on the precise concentration of carbon monoxide in 
the air that he is breathing. The symptoms that 
result will vary with the degree to which the hemo- 
globin is saturated with carbon monoxide. If the 
hemoglobin is 20 per cent. saturated the effects are 
practically unnoticeable to a normal healthy man, 
though headache may be caused by prolonged exposure 
or appear subsequently after reaching fresh air: even 
NO. 2783, VOL. IIT | 
with 33 per cent. saturation nothing of a really serious 
nature occurs, though nausea and headache may be 
felt after some time, and transitory giddiness and con- 
fusion will occur after any short and severe muscular 
exertion. As the saturation of the hemoglobin with 
carbon monoxide gets higher the symptoms rapidly 
become serious. With 50 per cent. saturation, giddi- 
ness, weakness and inco-ordination of muscular move- 
ment, failure of mental power, and diminution of 
acuity of vision and hearing are pronounced ; slight 
muscular exertion causes palpitation of the heart and 
undue breathlessness, and will probably result in 
partial or complete loss of consciousness for a time. 
Such a degree of saturation must therefore be regarded 
as definitely disabling, but, so far as is known, it will 
not prove fatal. If the affected person is removed 
to pure air the mass influence of the oxygen will 
gradually expel the carbon monoxide from the blood, 
and the more urgent symptoms will subside fairly 
rapidly, though nausea, severe headache, and malaise 
may persist for many hours. With still higher satura- 
tions complete .paralysis and unconsciousness will 
supervene, and the end may come with a painless 
death from sheer failure of the oxygen supply to the 
tissues of the body. 
The minimum concentration of carbon monoxide 
that will prove fatal is not known with certainty, but 
the available evidence points to the conclusion that 
death will ensue after an exposure for several hours 
to air containing o-2 per cent. of the gas. Much 
depends on the length of time that the blood has been 
highly saturated with carbon monoxide, for the longer 
grave shortage of oxygen is maintained the more 
serious is the damage to the tissues of the body, par- 
ticularly to the nervous system, and the more difficult 
is recovery. Bearing this in mind it is not improbable 
that o-15 per cent. of carbon monoxide in the air 
breathed might prove dangerous to life in the case 
of prolonged exposures. 
Exposure to relatively high concentrations of the 
gas leads, of course, to rapid loss of consciousness and 
death, but in accidental cases of poisoning the con- 
centration of carbon monoxide is, as a rule, com- 
paratively low, and in these circumstances the onset 
of symptoms will be gradual though progressive, for 
the gas owing to its low concentration will diffuse 
but slowly into the blood and it will be long before 
complete gaseous equilibrium can be established 
between the blood and the air in the lungs. Herein 
lies a great danger, for so insidious is the onset of the 
symptoms that the person affected may not realise 
that anything is amiss until he has lost so much power 
in his limbs as to render it impossible to withdraw 
from the danger. With o-r per cent. of carbon mono- 
oxide in the air breathed a resting person will become 
disabled in about two hours and a half, with o-2 per 
cent. in little more than a hour, and with o-4 per 
cent. in about half an hour. The acceleration of the 
respiration and circulation by muscular exercise will 
greatly hasten the rate at which carbon monoxide is 
absorbed into the blood. 
At present there is no legal limitation of the amount 
of carbon monoxide that may be supplied in ordinary 
