Thursday, April 15, 2010

Health and Ventilation

The public as well as health workers and0educational authorities are indebted to Dr.Wood and Mrs. Hendriksen for presenting in Ventilationt and Health the results of recent English and American investigations of the factors which make for good or bad ventilation of buildings as judged from the health standpoint.The scope of the book is limited to buildings; the ventilation of mines and tunnels is not treated.
It is only within the last 20 years that we have been brought to the realization that in general the health qualities of air are physical and not chemical; that attention must be paid to temperature, humidity and air motion rather than to the relative quantities of oxygen and carbon dioxide.

Following the presentation of this modern conception, the authors discuss ventilation practices, the ventilation of schools, end ventilation laws. It is pointed out that although comparative tests conducted in New York City Schools demonstrated that children in classrooms supplied with fresh air through open windows, showed significantly less respiratory illness than did children in rooms ventilated by mechanical systems, the laws and regulations governing the ventilation of schools in half our states provide that 30 cubic feet of (fresh) air shall be supplied for each child, each minute. Because this performance cannot be guaranteed, this requirement prohibits employing the open-windowgravity- exhaust system. Thus antiquated laws, based on a discredited and generally discarded theory, prevent thousands of children from enjoying the benefits of our present knowledge.

An accurate thermometer and its exposure where it will give representative readings for the occupied space, constitute the first step toward healthful atmospheric conditions in the classrooms. The second step, equally important, is to keep a permanent record of the temperature readings taken 6 or 8 times daily during the heating season. Merely providing thermometers will not correct overheating.Record-keeping focuses the teacher's attention
on temperature and remedial measures can be taken when overheating threatens.
The chapters on factory ventilation, ventilation for general use, ventilation costs and devices to aid ventilation appear inadequate. Further, they contain definite statements on controversial points, and so many references to the accomplishments of one particular worker in the field, as to give this section the character of a professional announcement.
To suggest that the intricate problem of adequately ventilating continuous-performance theaters in this climate (New York) throughout the year can be solved by employing modified window or any other system of natural or gravity ventilation appears unjustified. On the other hand, school auditoriums and churches, which are used intermittently and usually for relatively brief periods, may, under certain conditions of floor and air space, exposure and
outdoor temperature, be adequately ventilated by this method. No general rule can be given to govern all such cases, however; each separate problem must be studied and solved individually.
In their enthusiasm to emphasize the virtues of natural ventilation, it appears that the authors have fallen into the error of condemning mechanical ventilation in general. However true may be the opening statement in the last
paragraph on page 150-" The waste in ventilation begins with the installation of a mechanical system "-in numerous specific instances, the implication that systems of mechanical ventilation in buildings are always superfluous and wasteful is contrary to the daily experience of thousands of industrial plants and greatly weakens the force of the excellent advice in the paragraph that precedes it.
Descriptions of the sling psychrometer, the vane anemometer, and the recording wet and dry bulb thermometers might have been included to advantage in the chapter on Ventilation Instruments. The chapter on Educational Methods is filled with practical suggestions that will be welcomed by the average health worker.
Ventilation and Health is one of a very few books dealing with this newer knowledge of healthful ventilation, developed in England by Leonard Hill, and his coworkers of the Medical Research Institute, and in the United States by the New York State Commission on Ventilation, and more recently by the American Societv of Heating and Ventilating Engineers in their Research Laboratory, at the U. S. Bureau of MIines, and it is because of this, and the practical suggestions that the book is valuable.
That inaccuracies have survived the editing of this work; that descriptions of apparatus and procedures are often inadequate, and that personal opinions have at times been substituted for statements of fact, are to be regretted.

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