Breathing zone air pollutants

Air pollutants can be considered in three contexts pervasive air pollutants, indoor air pollutants, and breathing zone air pollutants. 

Breathing zone air pollutants Those air poUutants that are present in appreciable concentration only in a very smaU area, confined to the breathing zones of those immediately present Breathing zone air poUutants do not pose threats to others close by, even if they are in the same room or area. 

Another example of breathing zone air pollution is the use of theatrical fogs and smokes on stages and film sets. These are composed of aerosolized glycol ethers or mineral oil and are inhaled by actors during the course of their work. Health effects of such exposure include acute and chronic upper and lower respiratory ailments [12]. Theatrical fog and smoke aerosol exposure is not always limited to actors breathing zones. When large quantities of these are used in theaters, a confined space exposure is established and audiences are also exposed. 

Air pollution can be limited to the breathing zone, that is, the area within a short distance of the nose and mouth. Air pollution in the breathing zone... 

Scores are tied to the paths taken by the pollutants through the air. Wind condition, temperature, and relative humidity, however, vary widely so the same amount of pollution can have far different effects on different days or even at different times of the same day. Breathing zone concentrations of pollutants can range from acceptable to extremely toxic in the same location as a function of time. 

Local Exhaust Ventilation Local exhaust ventilation requires the management of much smaller volumes of air compared to general ventilation. Local exhaust systems capture contaminants at or near their source before hazardous substances reach the breathing zone of people. A system moves the air to locations where people will not be present. To meet air pollution standards, exhausted air may need treatment to remove and collect contaminants. 

When siting a capture hood or slot, advantage should be taken of the natural movement of the pollutants as they are released. For example, hot substances and gases are lighter than air and tend to rise, thus overhead capture might be most suitable, whereas some solvent vapours when in concentrated form are heavier than air and tend to roll along horizontal surfaces and pour downwards, so capture points are best placed at the side or below. Care must be taken to ensure that all contaminants are drawn away from the breathing zone of the worker - this particularly applies to places where workers have to lean over or get close to their work. It is important to note that whenever extract ventilation is exhausted outside, a suitably heated supply of make-up air must be provided to replace that volume of air discarded. 

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