Chamber Top assembly ventilation requirements vary according to the application.
Requirements for the levels of ventilation defined in BS EN 124 (minimum 5%/140cm2 of the frame Clear Opening) are unusual.
Most often, customers require the covers to ensure that gas pressure cannot accumulate within the associated chamber.
In pressure relief applications such as this, where full ventilation defined by BS EN 124 is not required, Wrekin add a series of 20-25mm dia. apertures to increase the open area of a manhole top provided by existing features of the products.
Note: Where pressure relief is offered for a particular product, Wrekin has notified BSi of the intended modification and verified that the modification will not compromise the ability of cover structures to withstand the loads required by the respective BS EN 124 category.
Where a large ventilation area is required (e.g. in excess of the BS EN 124 requirement), Wrekin recommends consideration of an unmodified gully grating product rather than structurally compromising a Chamber Top assembly with excessive ventilation apertures.
