I have prevented equipment from being bought without the correct Local Exhaust Ventilation of something like a Purex Heppa Filter unit with a large box filter.

Enginneer wanted to buy a Heppa Filter Vacuum Cleaner as it said it delivered the same air quality on exit.

My contention was that a vacuum cleaner will either block, bind or reduce the volume of air face velocity as the bag fills and ages. A large filter block would be less likely to do this. I am accused of gold plating safety!

We do not have access to an LEV system like a Donaldson Torrit.

Am I right in my assumptions? Is there supporting evidence out there?

What is the process you are trying to control? Unless you provide details of the contaminant, particle size, process conditions etc. no-one can answer your questions.

Actually regulation 7(1) of COSHH states: Every employer shall ensure that the exposure of his employees to substances hazardous to health is either prevented or, where this is not reasonably practicable, adequately controlled. Note that the phrase 'reasonably practicable' only applies to prevention; where prevention is not practicable exposure must be adequately controlled. Unfortunately, there are aspects of exposure where 'adequately controlled' is not well defined, skin exposure being the most significant.

With regard to LEV, design of the system is best left to someone who understands how LEV works. I come across many systems where, although they are working to the defined capacity, i.e. moving the quantity of air specified, they are failing to capture the contamination to the extent needed. A simple demonstration with a smoke tube will often provide graphic evidence of this. It is usually because no-one has correctly designed and installed the capture system. I doubt whether a vacuum cleaner would comply with this need.  Often the properly designed capture system would substantially reduce the amount of air movement needed and hence safe energy costs.

In addition one has to ask the questions: "What are we removing, how will we contain it and how will we dispose of it?" I doubt very much whether the person suggesting the vacuum cleaner is aware of how complex these can be and how important they are. 

LEV is best left to the expert.

Chris

Without knowing what you are dealing with or trying to prevent, its difficult to suggest how to sort it. There are various LEV systems that are mobile and designed to be moved between jobs. I have attached a link for one type, although these are mainly for welding fumes / wood dust. I should point out that other manufacturers are available!

http://www.nederman.com/en-gb/products/family/?catalog=24&category=1705