Informe De Prácticas Pre Profesionales

RESPIRATORY PROTECTION

15 RESPIRATORY PROTECTION
Introduction
In the course of their work, construction personnel are often exposed to respiratory hazards in the form of dangerous dusts, gases, fumes, mists, and vapours. In some cases careful selection of materials and work practices can virtually eliminate respiratory hazards. Where that is not possible, the next best choice is engineeringcontrols such as fume exhaust systems that deal with the hazard at the source. Respirators are the least preferred method of protection from respiratory hazards because they • • • do not deal with the hazard at the source can be unreliable if not properly fitted and maintained may be uncomfortable to wear.

jobs under way. For example, both mist and vapours may be present from paint spraying orboth gases and fumes from welding. Health Effects Respiratory hazards can be divided into the following classes based on the type of effects they cause. Irritants are materials that irritate the eyes, nose, throat, or lungs. This group includes fibreglass dust, hydrogen chloride gas, ozone, and many solvent vapours. With some materials (e.g., cadmium fume produced by welding or oxyacetylenecutting of metals coated with cadmium) the irritation leads to a pneumonia-like condition called pulmonary edema. This effect may not be apparent until several hours after exposure has stopped. Asphyxiants are substances which result in inadequate oxygen in the body. They can be classified as either simple asphyxiants or chemical asphyxiants. Simple asphyxiants are other gases or vapours which causeoxygen to be displaced, creating an oxygendeficient atmosphere. Oxygen content of 18% may lead to some fatigue during exertion. Oxygen concentrations lower than 15% can cause loss of consciousness and may be fatal. For example, nitrogen used to purge tanks can displace oxygen, resulting in unconsciousness and even death for those who enter. Oxygen may also be consumed by chemical or biologicalactivity such as rusting or bacteria digesting sewage. Chemical asphyxiants interfere with the body’s ability to transport or use oxygen. Two examples are carbon monoxide and hydrogen sulphide. Central nervous system depressants interfere with nerve function and cause symptoms such as headache, drowsiness, nausea, and fatigue. Most solvents are central nervous system depressants. Fibrotic materialscause “fibrosis” or scarring of lung tissue in the air sacs. Common fibrotic materials found in construction include asbestos and silica. Carcinogens cause or promote cancer in specific body organs. Asbestos is the most common carcinogen in construction. Nuisance dusts do not cause significant effects unless exposure is of high concentration and/or long duration. Excessive exposure to these substancescan be adverse in itself or can aggravate existing conditions such as emphysema, asthma, or bronchitis. Examples include plaster dust, cellulose from some insulation, and limestone dust.

In spite of these drawbacks, in many construction operations respiratory protective equipment is the only practical control.

Respiratory Hazards
Respiratory hazards may be present as • • • • • gasesvapours fumes mist dusts.

Gases — consist of individual molecules of substances, and at room temperature and pressure, they are always in the gaseous state. Common toxic gases found in construction are carbon monoxide from engine exhaust and hydrogen sulphide produced by decaying matter found in sewers and other places. Vapours — are similar to gases except that they are formed by the evaporation ofliquids (e.g., water vapour). Common vapours found in construction are produced by solvents such as xylene, toluene, and mineral spirits used in paints, coatings, and degreasers. Fumes — are quite different from gases or vapours, although the terms are often used interchangeably. Technically, fumes consist of small particles formed by the condensation of materials which have been subjected to...