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Dilution & Local Exhaust Ventilation for Shipyards

One of the major hazards associated with working in maintenance shipyards is the impact of poor air quality. Those working in confined spaces may be subject to stagnant air as a result of insufficient airflow or toxic and hazardous contaminants as a result of source pollutants.

Ventilation is required to ensure the correct level of oxygen needed to dilute and remove contaminants such as CO2 and hydrogen sulphide, in addition to comfort cooling or heating.

In general, there are two common methods of shipyard ventilation; Dilution Ventilation and Local exhaust ventilation.

Dilution ventilation can be used to reduce concentrations of flammable and toxic fumes, vapours, or particulates while maintaining sufficient oxygen levels. Dilution ventilation uses clean air (forced air) to dilute the contaminated air and then exhausts the diluted air to the outside via exhaust fans such as plate axial or plug fans. It should be noted that this type of ventilation does not eliminate exposure to toxic gases or vapours but merely dilutes the air to a suitable level of oxygenation. If toxic, the exhausted air should be completely transported to the outside and not recirculated. Dilution ventilation is rarely used in the shipyard industry for the control of atmospheric health hazards. However, dilution ventilation is frequently used for comfort, particularly in shops and other locations.

Local exhaust ventilation is frequently used in the shipbuilding industry and is the recommended method when workers are exposed to hazardous chemicals, when a large amount of dust or welding fumes are generated, or during cold weather when increased heating costs from the use of dilution ventilation is a concern. Local exhaust ventilation involves trapping airborne contaminants at their source before they contaminate the air that is breathed by workers. For welding, cutting and heating processes, this type of ventilation must consist of freely movable hoods placed by the welder or burner as close as possible to where the work is being performed. Local exhaust ventilation is based on the principle that air moves from an area of high pressure to an area of low pressure. The difference in pressure is created by a powerful industrial fan that draws air through the ventilation system. Toxic air and particulate is either passed to atmosphere or filtered away from the user.

Most shipyard work is performed in confined spaces and many of these operations produce copious amounts of smoke, fumes and gases. Without effective ventilation these contaminants would build to hazardous levels, affecting many workers. The success of occupational safety and health programs in shipyards very much depends on the proper use and maintenance of ventilation systems. For information about suitable industrial fans for use in shipyard ventilation including LEV, visit our website.

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