Wood Waste LEV

LEV System for Wood Waste – Case Study

March 15, 2023

The Vent-Tech team was asked by a third party company who had undertaken air monitoring to look at a couple of LEV systems for wood dust control at their site. They had quickly established that the existing systems were not providing adequate control of exposure to the wood dust with exposure levels recorded as high as 29.7mg/m3!

Whilst wood dust has a Workplace Exposure Limit (WEL) of 5.0mg/m3, as it is a known carcinogen and asthmagen. It is the legal responsibility of the duty holder to control exposure to As Low As Reasonably Practicable (ALARP).

The release of dust in the workshop and the fact that the explosion venting device was venting back into the workshop also raised serious concerns regarding compliance with the DSEAR Regulations (Dangerous Substances and Explosive Atmospheres Regulations).

How Vent-Tech Helped

Vent-Tech was initially engaged by the client to provide consultancy and advice on the best course of action.

Sweep points not recommended by HSE explosion vent relief filter plant inside wood waste workshop

The client had two workshops in separate locations, each with several tools and machines attached to them. The first action was a site visit during which we were able to discuss with the client the issues and concerns in detail and how they should be resolved. Our engineers followed this up with a short Survey Report to be presented to management, detailing where in the regulations and guidance the concerns raised originate from. From this, a detailed design was commissioned.

Our LEV Design for Woodwaste

The design report looked at the machines to be connected, and which ones were to be in use at any given time. We also took into account the exposure levels with no controls in place and, more importantly, the expected exposure levels when all controls are utilised.

This enabled us to give the client a guarantee of what the exposure levels will be once our new system was installed and that this could be independently verified by the third party occupational hygienist.

The design report included detailed:

  • Design drawing (showing hood designs and ducting layouts),
  • Filter plant details,
  • Air volume flow rates,
    ATEX Features,
  • Installation standards,
  • Electrical requirements,
  • Noise levels.


Installing the LEV Systems

new filter plant

The installation followed a few months later following a re-vamp of the workshops (combining the two into one).

The new filter plant was located external to the workshop. This helped reduce the operative’s exposure to noise and reduce the risk of secondary dust exposure in the event of dust passing through the filter.

The unit was fitted with a collection bin that could be lined with a PVC sack to allow safe disposal of the waste collected.

The explosion venting device was directed vertically upwards to ensure the safe dispersal of any potential flame.

An explosion non-return damper was installed to prevent any potential explosion from traveling back into the workshop.

All ducting installed is clipped together (to enable ease of access in the event of blockages) and earth bonded to prevent the build-up of static electricity in the duct material.

New hoods were installed on each of the machines in accordance with the ACGIH Guidance. The hoods had manual shut off dampers and Monitair Chevron air indication devices. This meant that operatives were able to open

and close branches to suit, with clear indicators if they have too many points open.

connections to equipment using cup together ducting


Testing the Woodwaste LEV Installation

A smoke test was carried out to show the airflow patterns, whilst this showed air flowing into the hoods this was insufficient to prove complete control effectiveness.

To prove control effectiveness, air monitoring was carried out. Once we were happy control was being achieved, we invited the independent third party back in to prove the control and for the client to witness the results.

Using a TSi Dustrak direct reading dust meter, the hygienist carried out multiple readings around the operators working position whilst they carried out multiple jobs over a period.

At no point did the exposure levels reach anywhere near 1/10th of the WEL for wood dust enabling them to say adequate control was being achieved.

‘Very glad to see the major improvements since we started this project.


The maintenance staff are very pleased with the results and knowing it will be beneficial to their health just makes it all that better.


I must thank you and your team not only for the professional service but continuing to…I would however be happy to recommend you if asked’

At Vent-Tech we take on unique dust and fume problems regularly, and our highly trained engineers understand that when it comes to LEV one size doesn’t fit all. If you are noticing issues with your LEV systems, or just want

some piece of mind, then get in touch today.