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sure steam chamber, with a hot air blast, made by Messrs. Goddard, Massey, and
Warner, of Nottingham. The new chamber came into use at the end of October,
concurrently with the commencement of the Infectious Diseases Notification Act.
This chamber is rectangular, with the angles rounded, in order to avoid lodgement,
and give additional strength. Its internal dimensions are—height 5ft.,
•width 5ft., length 6ft. 6in.
It is entirely surrounded by a double jacket, and the doors are also double
jacketed. The space (about 4 inches) between the two jackets is filled in, the
lower half by water, and in the upper half and in the doors the steam circulates.
The water is heated by a furnace underneath, it takes about an hour to get up
steam. A safety valve is situated on the top of the chamber.
Steam is admitted into the chamber from the jacket through a screw down
valve, and it is withdrawn from the chamber through a screw down valve by a
steam exhaust pipe discharging into the chimney.
Two dial pressure gauges over the door mark the pressure and temperature
in the jacket and in the chamber respectively.
A supply of hot air is laid on through a channel furnished with baffles and
running at the back and along the side of the furnace, and discharging through a
screw down valve into the Chamber. This pipe, at my suggestion, has been
furnished with a thermometer to mark the temperature at which the hot air is
admitted, and the temperature is regulated by a cold air supply tap which has
been also attached.
The apparatus is worked in the following manner. Having raised the steam in
the jacket to 201bs. pressure, the chamber is charged with the articles to be sterilised,
and the doors are clamped.
The exhaust valve is opened and also the hot air valve, by this means the
cooler air is withdrawn from the chamber and displaced by the current of hot air.
This seems to thoroughly dry the articles and to displace the cooler air from their
interstices which otherwise might cause condensation of the steam.
The hot air valve is now closed and the steam supply valve opened, and then
the exhaust valve is closed. In about ten minutes a pressure of 20lbs. and temperature
of 260° F. is marked in both chamber and jacket. The steam supply
valve is now closed and the exhaust opened until the pressure gauge of the chamber
runs down to zero. This intermission only occupies about one minute, and is
necessary to insure complete penetration by the steam.
The exhaust is now closed and the steam valve again opened; in another ten
minutes the two gauges will both be found to mark 20lbs. pressure and a temperature
of 260° F., with a temperature of at least 212° F. in the interior of mattresses,
pillows, and other bulky articles. This has been repeatedly proved by actual
experiments.
The steam valve is now closed, and the exhaust valve and the hot air valve
are now opened to drive out the steam. This accomplished, the chamber is opened
and the articles taken out the opposite end to which they were introduced into a
separate room free from infection and infected articles.