A recent client visit highlighted a major health and safety issue, where chemical fumes from several cupboards were re-entering the building due to poor installation and discharge practices.
Upon inspection I discovered that the duct discharge stacks were both unsafe (and non-compliant) for the following reasons:
- Not high enough. BS EN 14175 states that duct discharge stacks must extend to 3 Metres above the highest point of the building or 1.25X the total height (whichever is greatest). Fumes were going back into the building via adjacent windows – some less than 10 feet from the discharge!
- No Reducers (or Gatherers). Reducers increase the discharge velocity to ensure the fumes are carried safely away.
- Fans located inside the building – internal ductwork under positive pressure resulting in leaks
So why does this happen?
- Installer either not aware of regulations or chooses to ignore them (“I have been doing it this way for years”)
- Less duct and fans located internally = less cost. We have lost projects in the past on price only to be contacted by Clients post-project to rectify installation issues
- Architects prefer streamlined buildings with no visible duct stacks but function HAS to take priority over Fashion when it comes to Toxic fumes.
- Planning Permission. It may sound crazy but Permission may be required for duct stacks and this takes time. It is “easier” and “cheaper” to just install a non-compliant stack(s)…
So what is my point?
Ask your Supplier/Installer if the system they are proposing will comply with BS EN 14175 – and then check the basics:
- Fans located externally?
- Duct discharge 3M above highest point of building or 1.25X total building height or discharge velocity increased to well above 10M/s?
- Duct material? Should be PVC or PP. NOT Galvanised.
- Duct Reducer(s) fitted?
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