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The employee's lungs can be considered as gaseous exchange units basically inspiring
atmosphere made up volumetrically of oxygen 20.96%. nitrogen 79%, carbon dioxide 0.04%; alveolar
air contains oxygen 14%. nitrogen 80%, carbon dioxide 6% and expired air contains oxygen 16.03%,
nitrogen 79% and carbon dioxide 4.4%. On an average this chemical exchange takes place sixteen
times each minute with an average inspiration and expiration, at rest, of approximately thirty
cubic inches,
Simple mathematics show that at rest each person converts, on average three-quarters of a
cubic foot of oxygen to three-fifths of a cubic foot of carbon dioxide each hour
Attention is now drawn to other factors or reasons tor changing air in an enclosed space.
Such considerations are body odours, scents, smoking and other contaminants known to the
process of living and working bacteria-carrying particles, viruses and products of combustion, and
the control of humidity and temperature have to be taken into account.
In years past the office was an enclosed space with a window a fire-place and a chimney
flue. Modernisation brought, first, central heating by water pipes, and then atmosphere was blown
into the enclosed spaces pre-heated or pre-chilled. Finally, in recent years in order to save monev
the recirculation of air/mixture back to the offices after use was introduced. This recirculation
is usually achieved by a split duct in the plant room, by means of which a proportion of the
vitiated air is exhausted to atmosphere and the remainder is re-used
There are two aspects of this recirculation system of importance.
Knowing that people give off a known quantity of waste gases (carbon dioxide) it is impossible
to avoid an increase in the carbon dioxide content of the mixture, whatever volume of
atmosphere is mixed with it in the plant room. Mathematically, this increase can be calculated
when the volumes and percentage of recirculation are known, as well as the decrease of the
oxygen.
Furthermore, where a recirculation system is installed, usually the plant provided has the
capacity to deliver adequate quantities of fresh air as the designers usually give the volumes of
mixture up to and above the ventilation recommendations of the Corporation.
Great care is devoted to ensuring that we have a pure water supply and no one would suggest
that in the interests of economy we should be doomed to drink polluted water even though the
pollution which has taken place cannot always be proved to be deleterious to health. In the
interests of economy, are lower ventilation standards to be permitted
In the City which has a very large daytime population and upwards of five thousand in a
single building, the standard set out above, for the reasons given, has been advanced as being
desirable and complying with the provisions of Section 7 of the Act of 1963. At the same time,
it has been made known that the Health Department is prepared to discuss the above standard
with anyone.
On a combined atmosphere heating/ventilation scheme the approximate cost is made up as
follows:-
Ventilation 7% - 20%
Heating 93% - 80%
of whole scheme
Section 6 of the Act provides for a temperature of 16° C or 60.8° F after the first hour.
In practice the operative temperature is normally set at 21.1° C or 70° F without any real reason
given for such a level of temperature. This central-heating setting is approximately 10° F above
the requirements of the Act of 1963. With heating/cooling requirements using so great a proportion
of running costs there would appear to be grounds for investigation as to what is a reasonable
setting of thermostats in central heating systems. This factor is of increased importance
as the only objection so far advanced against the 3000 cubic feet of atmosphere "through"-type
of ventilation has been the cost factor.
It is very important to place in their true perspective the responsibilities set out in the Act
between occupiers and owners. As an example; the occupier is responsible for ventilation of
premises in which persons are employed to work. How is the occupier of a suite of offices in a
tower block to effect improvement in ventilation if so required by the enforcing authority? This
does emphasise the desirability of consulting with a Local Authority before embarking on a major
project.
It is difficult to appreciate the extent of the work of the department purely in statistical form
when emphasis has been placed on prevention rather than cure. For example,one Inspector was
engaged exclusively on ventilation problems within the City for the second half of the year.
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