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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.
The Control of Substances Hazardous to Health Regulations 2004 (C.O.S.H.H.) requires employers to prevent, or where this is not reasonably practicable, to adequately control the exposure to their employees to substances hazardous to health. The measures that an employer introduces to control exposure are required to be maintained in an effective condition and be examined and tested at regular intervals. In the case of general local exhaust ventilation systems the frequency of the thorough examinations and testing is every 14 months.
In addition it is recommended in the approved general code of practise that all such systems are inspected on a regular basis (weekly) and that all such inspections are recorded together with any actions that have been taken. The inspections recommended are intended to be inspections which could be carried out by the workforce and could include inspections of duct work for damage or blockage etc. The aim of all of the above is to ensure that the local exhaust ventilation system is performing its intended role and to ensure that defects are identified and corrected promptly.
All records with regard to local exhaust ventilation systems have to be maintained for at least 5 years.
EXAMINATION AND TESTING CRITERIA.
In essence, ideally, all local exhaust ventilation systems should consist of the following main elements;
A capture hood to collect and contain the contaminant.
Duct work to convey the contaminants away from the source.
Air cleaning device to remove the contaminants.
Fan or other air mover to provide the necessary airflow.
Duct work to convey the cleaned air to the outside atmosphere.
Of the above it is the design of the capture hood is of primary importance and should be designed so that;
As much as possible of the source of emission is enclosed.
The air velocity at the source of emission is sufficient to capture
the contaminant.
The Health and Safety Executive in the following publications HS / G 37 " An introduction to Local exhaust Ventilation" and " The maintenance, examination and testing of local exhaust ventilation" provide guidance on criteria which should be meet both in the performance and management of such systems.
The performance criteria include the following;
CAPTURE VELOCITIES.
| CONDITIONS | EXAMPLES | CAPTURE |
| DISPERSION | VELOCITY m/s | |
| OF CONTAMINANT. | ||
| RELEASED WITH | EVAPORATION | 0.26 - 0.50 |
| PRACTICALLY NO | FROM TANKS. | |
| VELOCITY INTO QUIET | ||
| AIR. | ||
| RELEASED AT LOW | SPRAY BOOTHS | 0.50 - 1.00 |
| VELOCITY. | WELDING. | |
| PLATING. | ||
| ACTIVE GENERATION | SPRAY PAINTING. | 1.00 - 2.50 |
| INTO ZONE OF RAPID | BARREL FILLING. | |
| AIR MOVEMENT. | ||
| RELEASED AT HIGH | GRINDING, ABRASIVE | 2.50 - 10.00 |
| VELOCITY INTO | BLASTING, TUMBLING | |
| ZONE OF VERY RAPID | ||
| AIR MOTION. |
DUCT VELOCITIES
| CONTAMINANT TYPE | DUCT VELOCITIES m/s |
| GASES | NO MINIMUM |
| VAPOURS, SMOKE, FUME | 10 |
| LIGHT/ MEDIUM DENSITY DUST | 15 |
| SAW DUSTS. | |
| AVERAGE INDUSTRIAL DUSTS | 20 |
| GRINDING DUST | |
| HEAVY DUSTS | 25 |
| LEAD, METAL TURNINGS. | |
The required management criteria can be summarised as follows;
Maintenance of the systems in effective working condition.
Carrying out or having carried out on their behalf the statutory examination and test procedures.
Weekly visual checks and where appropriate for more frequent inspection and monitoring.
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.
Similar to all other Health and Safety Legislation the onus of proving compliance lies with the employer and therefore any organisation should develop or alter existing management systems so that the pertinent information is available for inspection by the enforcing authorities.
