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FIRST REPORT
TO THE
MAIN DRAINAGE COMMITTEE OF THE LONDON COUNTY COUNCIL,
ON
SEWER AIR INVESTIGATIONS.
By J. PARRY LAWS, F.I.O.
To the Main Drainage Committee, London County Council.
Gentlemen,
I beg to present to you my report of the investigations on sewer air, which I have been carrying
out in accordance with your instructions in the King's Scholars Pond sewer.
Although sewer air has for a long time been regarded as dangerous, and a likely source of
infection in certain specific diseases, very little has been done to substantiate this hypothesis by
scientific research.
The earliest experiments on sewer air are those of Dr. Letheby, in 1857-58 (Report to the
City of London Commissioners of Sewers). He examined the air in thirteen sewers of the City of
London, and found the following—
Marsh Gas and 140 grains of air deprived
0% N% Vols, of C02 Sulphuretted Ammonia of co2 and H2 O gave on
per 10,000. Hydrogen. Oxidation CO2 H20
19.506 79.962 52.2 Traces rather abundant 1.417 1.126
No indication of the condition of the sewers is given.
In 1867, *Dr. Miller, in the course of an investigation on the action of charcoal air filters, made
a number of analyses in two London sewers. One sewer was clean and well ventilated, the other
tide-locked and ill ventilated. In the former he found as the average of 18 analyses 10.6 Vols.
CO., and in the latter, as the average of 6 analyses, 30.7 Vols. C02 in 10,000. No sulphuretted
hydrogen could be detected.
In 1877, Beetz,† of Munich, found 31.4 Vols. C02 and 2.2 Vols, ammonia per 10,000 as an
average of 5 analyses.
The first determinations of micro-organisms in sewer air were made by Miguel.‡ He found 0.8
to 0.9 per litre in the sewer air of the Rue de Rivoli in the neighbourhood of the point where this
sewer joins the large collector of the Boulevard Sebastopol. He states that the organisms in the air of
the Rue de Rivoli may in summer exceed in number the organisms in the sewer air by five or six times,
whereas in winter the ratio may be reversed. No details, however, are furnished of the condition or
means of ventilation of the sewer.
The most important, however, and the most recent investigation on this subject is that of
Drs. Carnelly and Haldane. These authors made a series of observations in the main sewer of Westminster
Palace and in various sewers in Dundee.
In the Dundee sewers, by far the most important series of experiments, ventilation is carried out
by means of open gratings placed in the roadway at distances of about 50 yards apart, and also by open
drain grids placed along each side of the road, at distances of about 40 yards. The size of the sewers
ranged from 3 ft. 5 in. to 9 ft. The authors determined simultaneously the amount of C02, organic
matter, and the number of micro-organisms in the sewer air, and also in the fresh air above, as nearly
as possible at the same time.
The methods employed by them were for the estimation of C02 Pettenkofer's, for organic matter,
Carnelly and Mackie's modification of the permanganate process, and for micro-organisms, Hesse's
method. The general conclusions are as follows—
1. The air of sewers was much better than one might have expected.
2. The CO. was about twice, and the organic matter about three times as great as in the
outside air at the same time.
3. The number of micro-organisms was less in sewer air than iu the outside air at the
same time.
4. That in reference to the quantity of the three constituents above-named, the air of
sewers was in a very much better condition than the air of naturally ventilated schools, and,
with the exception of the organic matter, of mechanically ventilated schools.
5. Sewer air contained a much smaller number of micro-organisms than the air in any
class of house they had investigated.
* "Chemical News," March 13th, 1868.
† Quoted by Erismann in Pettenkofer and Ziemsen's "Handbuch dor Hygiene," vol. 2, p. 197.
‡ " Les Organismes Vivants de 1'Atmosphere, 1883," p. 273.