EFFICIENT, COST EFFECTIVE; HEALTH, SAFETY AND ENVIRONMENTAL MANAGEMENT SOLUTIONS.

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RISK ASSESSMENTS, HAZOP - FMEA- ETA- HRA STUDIES, 5s, HEALTH SAFETY ENVIRONMENTAL MANAGEMENT SYSTEM- FORMULATION- INTEGRATION- DOCUMENTATION- SUPPORT, AUDITS, EDUCATION AND TRAINING, OCCUPATIONAL EXPOSURE MEASUREMENT, CONTROL FORMULATION, LOCAL EXHAUST VENTILATION TESTING AND EXAMINATION

LOCAL EXHAUST VENTILATION.

Local exhaust ventilation (L.E.V.) systems are designed to remove contaminants at source before they enter the general atmosphere of the working area or the breathing zone of the operator. An L.E.V. system will normally comprise of a hood placed near to the source of contaminant, a section or sections of ductwork, air cleaning device and a fan which will draw air from the contaminant source and discharge to atmosphere. Like all equipment supplied for work purposes they must be fit; for purpose, the work environment and the users

Basic considerations

a) The type of hood used has to be suitable for the work process. A basic principle to adhere to is that the contaminant should not enter the breathing zone of any person working near the contaminant. This is normally achieved by either placing the extract system close to the contaminant source (so that the contaminant is captured before it has chance to rise to the breathing zone) or by enclosing the work/contaminant (in effect placing a barrier between the person and the process).

There are three basic types of extract hood:

• receptor hood - here contaminants enter the hood under their own volition. These hoods are normally suitable for slow moving contaminants.
• captor hood - here an air flow sufficient to change the direction of the contaminant is used.
• LVHV (low volume high velocity) hood - these tend to be used for energetic particles.

The design of the hood affects the airflow rate required in simple terms the greater the degree of enclosure the lower the air flow that is required

b) ductwork must be designed so that the air velocity is high enough to keep the contaminant airborne and any directional changes and dimension change are kept to a minimum.

c) If air cleaners are used they must be suitable for the operation. Different types of filters are available, e.g. high efficiency filters for ultra clean operations, filters fitted with chemical absorbing properties, etc.

d) The L.E.V. must be fitted with an appropriate fan, Centrifugal fans and normally used for L.E.V. systems.

e) L.E.V. systems have to be tested every 14 months by a competent person. Each L.E.V. system should have a unique identification number and when tested a report will be produced stating whether the airflow is adequate and if not what actions need to be taken.

f) All L.E.V. should have an indicator to show it is functioning properly. The simplest way to provide an indication that the extract is working is to attach a short piece of indicator tape to one of the top corners of the hood. Users of L.E.V. should check daily that the equipment is functioning - this can simply be done by looking at the indicator tape.

Selecting an L.E.V. supplier

Employers are responsible for choosing a competent L.E.V. supplier.

A clear specification will help you get what you need, and avoid any misunderstandings with the LEV supplier.

The specification should:     

• describe the process, the contaminant, its hazards and the sources to be controlled, and how stringent the control needs to be. The important chemical and flammable properties of substances and products appear in the Safety Data Sheet;
• require indicators to be fitted to show that the system is working properly;
• require the LEV to be easy to use, check, maintain and clean, taking account of other risks, e.g. accessibility, skin contamination, and waste removal and filter changing without spreading contamination; specify that the supplier provides training in how to use, check and maintain the LEV system;
• require the supplier to provide a user manual that describes and explains the LEV system, how to use, check, maintain and test it, along with performance benchmarks and schedules for replacing parts;
• require the supplier to provide a logbook for the system to record the results of checks and maintenance

Therefore, along with a detailed specification prior to carrying out the work there are three documents that you must receive from a supplier:

• User manual - (includes a general description of the system, commissioning information, list of replaceable parts, statutory testing requirements and a description of how it should be used properly).
• Logbook - (includes schedules and records of regular checks and maintenance).
• Commissioning report - (includes performance specification and results).

Example performance Criteria

CAPTURE VELOCITIES.

DUCT VELOCITIES

Basic management criteria;

• Maintenance of the systems in effective working condition.
• Carrying out or having carried out on their behalf the statutory examination and test procedures.
• Where appropriate for more frequent inspection and monitoring
• Daily visual checks
• Suitable systems for reporting and rectifying faults either identified at the time of the statutory examination and test or during the ongoing assessment of performance.

• EFFICIENT, COST EFFECTIVE; HEALTH, SAFETY AND ENVIRONMENTAL MANAGEMENT SOLUTIONS.