With more stringent legislation governing exposure limits and emissions to atmosphere, companies are having to look more closely at the efficiency of extraction systems.
Local Exhaust Ventilation or LEV falls within the Control Of Substances Hazardous to Health (COSHH) Regulations and can be divided into four main categories.
- Receptor systems where the contaminant enters the system without inducement. The fan in the system is used to provide airflow to transport the contaminant from the enclosure through the ducting to a collection system.
- Capture systems where the air flows into the hood capturing the contaminant outside the hood and induces it to flow into the system.
- Low volume high velocity where air extracted at high velocity through small apertures close to the source of contaminant.
- Dilution ventilation is used where it is not possible to extract the contaminant close to the point of origin. Used where the level of contaminant is small and the toxicity is low it may be possible dilute the fumes by inducing large volumes of air through the contaminated area.