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 we 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?
- The installer was either not aware of regulations or chose to ignore them ("I have been doing it this way for years").
- Less duct and fans located internally results in 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 our point?
Ask your supplier/installer if the system they are proposing will comply with BS EN 14175 – and then check the basics:
- Are the fans located externally?
- Is the duct discharge 3M above highest point of building or 1.25X total building height or discharge velocity increased to well above 10M/s?
- What is the duct material? It should be PVC or PP, NOT galvanised.
- Are duct reducer(s) fitted?
TION can help you create the safest & most professional working environment for staff and clients, ensuring you conduct your processes, research or experiments to the highest standards. Get in touch with our team today if you have questions about your ductwork installation or discharge systems.