A well-designed LEV system removes airborne contaminants at or near their source and prevents spread to the wider workplace. For construction and refurbishment, that often means task hoods, short duct runs, effective filtration and clear user checks.

Step 1: Define the problem

• Identify the substance and task: silica from grinding, hardwood dust from sanding, or mixed demolition fines.
• Decide if capture must be on-tool, a fixed capture hood, or partial enclosure based on access and dust release.

Step 2: Set the capture approach

• On-tool or close-capture hoods minimise airflow demand by working near the source.
• Where feasible, enclose: simple screens and strip curtains improve capture and protect others.

Step 3: Size airflow under load

• Choose fans and vacuums based on required capture, not free-air ratings. Account for pressure losses from hoses, filters and bends.
• Keep ducts short and smooth, with gentle bends, to preserve transport velocity and prevent dust settling.

Step 4: Filtration and discharge

• Select filtration to the hazard: M-Class for general wood and mineral dusts; H-Class or H14 where respirable or carcinogenic dusts are present.
• Position discharge to avoid re-entrainment; consider negative air to maintain flow from dirty to clean areas.

Step 5: Controls, testing and records

• Provide simple user checks: airflow indicators, filter status and a clear fault response.
• Commission with visualisation (smoke) and basic measurements at hoods. Record settings and capture distances.
• Plan maintenance: filter changes, duct inspections and cleaning. Keep spares and a schedule.

Step 6: Integrate with housekeeping

• Use industrial vacuums for clean-up; avoid sweeping and compressed air.
• Bag and seal waste at source to prevent re-release.

Compliance context

COSHH expects exposure to be prevented or adequately controlled, and HSE guidance stresses capture at source where reasonably practicable. Design choices that reduce dispersion make meeting Workplace Exposure Limits far easier.

Practical takeaways

• Bring the hood to the source; short, smooth ducts beat long, leaky runs.
• Specify by under-load performance and the necessary filtration class.
• Set up clear user checks and maintain records from commissioning onward.

LEV that is close, simple and maintainable will outperform complex systems in the real world. Focus on source proximity, under-load airflow and disciplined upkeep.