Extract ventilation

Use with proper local extract ventilation or, as a minimum, in a well-ventilated area Replace lids on buckets, waste bins and troughs... 

A factory building (Fig. 11.43) consists of two spaces a hall with mechanical extract ventilation for combined abrasive and chemical treatment and subsequent bonding and a naturally ventilated assembly hall. 

VOCs are released during chemical cleaning of bonding surfaces. The extract system is designed on the basis of the steady-state concentration determined for maximum source strength and considering the mechanical extract ventilation only and no air-exchange with the assembly hail. Ehis concentration must be kept below the threshold concentration (TVL) which is set to 300 mg/kg in this example. 

Extract ventilation The mechanical ventilation arrangement to extract polluted air away from a space, either directly or by means of ductwork. 

Fan-assisted balanced ventilation. Supply or extract ventilation within a space designed to provide the correct ratio of supply to extract air by means of one or more fans. 

Fan-assisted exhaust ventilation Extract ventilation of a space by means of a fan, with the supply air provided by induced leakage into the building. 

Ventilation can be provided as general dilution ventilation or local extraction ventilation. 

Handle in well-ventilated area, preferably with hood equipped with forced extract ventilation. 

This document [63] also suggests exposure control measures in the following hierarchical form eliminate (i.e. avoid using hazardous substance), substitute (i.e. replace with less risky material), enclose (i.e. perform operations in enclosed cabins), engineering control (i.e. carrying out potential dust formation processes with extract ventilation), procedural control (i.e. limiting the number of personnel exposed, their time and the process to specified areas), and personal protective equipment (i.e. use of protection measures to limit inhalation and dermal exposure). 

Where it is not practicable to enclose the process totally, other steps must be taken to contain contaminants. This can be achieved by removing vapours, gases, dusts and fumes etc. by means of a local extract ventilation system. Such a system traps the contaminant close to its source and removes it so that nearby workers are not exposed to harmful concentrations. 

Local extract ventilation systems have four major parts ... 

There are several different types of local extract ventilation systems and adherence to sound design principles is necessary to achieve effective removal of contaminants. Ventilation systems must also be adequately maintained to ensure that they are operating to design specifications. This subject is dealt with in greater detail in Chapter 21. 

In the design of extract ventilation it is important to create, at the point of release of the pollutants, an air velocity sufficiently strong to capture and draw the pollutants into the ducting. This is known as the capture velocity and can be as low as 0.25 m/s for pollutants released gently into still air such... 

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. 

Plant that is subject to periodic statutory inspections includes lifting plant for both goods and people and associated ancillary components, boilers, pressure vessels, power presses, extract ventilation plant and some electrical installations in special situations. A list of the principal Regulations containing plant inspection requirements is given in Table 29.1. 

If necessary extract ventilation should be fitted to the wheel encasing to remove dust at source. 

Extraction ventilation will be required for the wood dust and shavings both above and below the saw table. 

Dust and chippings should be removed by efficient extraction ventilation and use vacuum for cleaning. 

The non-electrical safety precautions comprise protective clothing for the operator to prevent burn injuries from arc sputter and the ultraviolet and infrared radiation produced by the arc. A visor is used to protect the face, with an aperture fitted with a filter glass through which the operator observes the area. It is usually necessary to provide extract ventilation to remove fumes, and opaque or filter screens, arranged around the operator, to protect other people in the vicinity from ultraviolet radiation (see Fig. 16.2). 

It s significant to know that pressure in gas supply lines within machinery spaces is less than 10 bar. Full penetration butt joint is one of the obvious features of Increased type. In addition, anywhere in machinery spaces including GVU is covered by two sets of gas detectors. As far as ventilation is concerning, the air space within the machinery spaces and GVU are equipped with mechanical extraction ventilation having a... 

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