View report page

40
Tunnels
Ventilation of tunnels, buildings, etc.
To provide a check on the functioning of the ventilation plants at Blackwall and
Rotherhithe Tunnels, systematic weekly examination of the air is undertaken by the
Chemical Branch. The times chosen for the tests are those when the tunnels are
normally carrying their heaviest traffic. Measurements are made of the carbon monoxide
content, the amount of black suspended matter and the temperature and humidity of
the air.
The volume of motor vehicle traffic in both tunnels has increased every year since the
war and in 1953 it equalled the pre-war level in Rotherhithe Tunnel and considerably
exceeded the pre-war figures in Blackwall Tunnel. The tests indicated that the amount of
forced ventilation had been efficiently adjusted to meet the variations in traffic and, of
202 air samples only 4 at Blackwall and none at Rotherhithe contained carbon monoxide
in excess of the specified limit of 250 parts per million.
The use of tetra-ethyl lead in petrol produces traces of lead compounds in the air
of the tunnels and nitrous fumes from diesel engine exhausts can also be detected.
Special tests made during the year showed that the amounts of these contaminants were
well below the accepted toxic concentrations.
Underground
workings
When exploration was made of a large system of underground chalk workings
which had caused subsidences, analysis of the air showed some deficiency of oxygen and
also the presence of carbon dioxide in excess of the normal concentration. Advice was
given on the appropriate safety measures to be taken.
Petrol
leakage
Several cases or accidental leakage of petrol from storage tanks were investigated
and ventilation tests were made of neighbouring premises to ensure that suitable precautions
were taken against the presence of petrol vapour in the atmosphere.
Factory
In co-operation with H.M. Inspector of Factories, tests were made of the atmosphere
of a factory licensed to use petroleum spirit. It was found that conditions in a machine
room called for an improved system of ventilation and a suitable ventilating plant was
subsequently agreed upon.
Royal
Festival
Hall
Advice was given on matters relating to the ventilation of the Roval Festival Hall.
Gas
heaters
Consideration was given to the use of flueless gas heaters and the degree of ventilation
needed to avoid perceptible vitiation of the air of rooms.
Fire : precautions and investigations
A number of types of material were examined for their quality and suitability for
use in the fire service; these included rubber hose, foam producing compounds and
chemical extinguishers. Fire retardant compositions for application to building materials
were examined for efficacy in preventing flame spread and a practical test was formulated
to serve as the criterion of fire-resistance where safety regulations called for
fireproof curtain material.
Advice was given on miscellaneous problems, of which the following are examples :
In co-operation with Fire Brigade officers, detailed consideration was given to
the special measures needed in combating fires involving dangerous chemicals.
The routine procedure for maintenance of foam extinguishers was reviewed
at the request of the Chief Officer of the Fire Brigade and it was found that a saving
in cost could be effected by a modification which was subsequently approved by
H.M. Inspector of Fire Services.
Recommendations were made on the degree of flame-proofing necessary for a
diesel-engined crane to be operated at a petroleum wharf.
After examination of conditions at a pumping station, advice was given that it
was unnecessary to incur the expense of a flame-proof electric motor in the particular
circumstances of this case.