NSHEVs are installed in the roof to provide essential ventilation in the event of a building fire. They open, either by sensors or remote control, to exhaust smoke and noxious fumes. It is a simple concept, utilising simple physics, to make a dangerous situation safer and it is applicable in almost all building typologies from auditoriums, to universities, to warehouses.
James Fisher, MD of Bilco UK, Howe Green and Profab Access outlines the top three considerations that building services professionals should take into account when specifying NSHEVS.
It is a common misconception that in a building fire the biggest threat to life arises from the flames. In actual fact it is the silent, pluming black smoke. A fire spread by convection is the most dangerous and is the cause of the largest number of injuries and deaths.
In a situation where a fire starts in an enclosed space the smoke rising from the fire gets trapped by the ceiling. At this point the smoke will spread in all directions and form an expanding layer over the whole space, leaking into any gaps in the walls or floors.
NSHEVs protect building occupants by preventing the excessive build-up of smoke and noxious fumes. By exhausting smoke, NSHEVs reduce the risk of smoke inhalation and damage, horizontal fire spread and secondary ignitions. In the event of a fire they also improve visibility accelerating evacuation times and assisting fire-fighters.
If you are a specifier you have a responsibility to ensure the right product is used in the right context and it is of the right quality. As we are all aware, in construction ensuring the right product for the right context is crucial, the consequences of making the wrong decision can be catastrophic.
When specifying a NSHEV it should be fully compliant with the Construction Products Regulation 305/2011, CE-marked with a Declaration of Conformity and manufactured to meet the demands of Building Regulations, Approved Document B, BS9999 and BS EN12101-2.
These important accreditations and certifications are evidence for the operational reliability, high quality and performance of the NSHEV.
There are many design options to consider when specifying NSHEVs, from both an aesthetic and operational perspective.
A choice of hardware, paint finishes, curb liners, manual and automate control units, open-close switches and rain and wind sensors result in the creation of a customised NSHEV which is fit for purpose in your particular installation environment.
Utility and functionality are key. An NSHEV that can address a range of problems is cost-effective and efficient, removing the need for additional roof penetration. NSHEVs can be used for comfort ventilation as well as for exhausting smoke. The option to fit rain and wind sensors allows the ventilation system to close open vents in the case of inclement weather.
With some simple modifications, such as the addition of a fixed vertical safety ladder, an NSHEV can provide a means of escape from the roof or offer access for infrequent maintenance. By using a skylight the NSHEV can also offer a source of natural daylight to the space below.
Careful consideration is required into how the NSHEV will be controlled in the event of a fire. Will a stand-alone management system suffice or do you require a solution that can be integrated into a fully networked fire alarm or Building Management System?
To summarise, specifying Natural Smoke and Heat Exhaust Ventilators might not be “sexy” but it is critically important. Ensure that you choose a quality product that has been designed and manufactured to satisfy the required legislation and that addresses the specific technical challenges in your project.