Locate the point of release
Local exhaust ventilation aims to capture contaminants near the activity that releases them. General ventilation works across a larger space, mixing and replacing room air. The distinction is the location and method of control.
For a laboratory procedure inside an enclosure, a fume cupboard can provide local extraction. A room fan does not automatically provide the same capture at the working opening.
Compare the design questions
| Local extraction | General ventilation |
|---|---|
| Where is the substance released? | How does air move across the room? |
| Can the task be contained at its source? | Where does replacement air enter? |
| What exhaust duty does the device require? | How do supply and extract systems interact? |
| How will users recognise a capture problem? | How will room conditions be controlled? |
The LEV system guide explains the equipment path. The laboratory ventilation guide covers the room-level coordination.
Use the risk assessment to choose controls
Describe the substance, task, release pattern and people who may be exposed. Include normal work and foreseeable variations. Your competent safety and ventilation advisers can then determine the appropriate control strategy and how its effectiveness will be assessed.
Keep that decision separate from a simple equipment capacity comparison. Moving more room air does not demonstrate effective capture at a particular procedure.
Write a coordinated enquiry
- Describe the process and provide relevant safety data sheets.
- Mark the task location, doors and air outlets on a plan.
- Identify existing extraction and room ventilation equipment.
- Explain whether the project is new work or a change to an existing task.
- Name the people reviewing exposure control and building services.
For an enclosed chemical task, our Calibre cupboard comparison can help the team discuss suitable equipment after the control requirements are established.