Smoke Control systems and the function of SHEVs
Smoke control is essential to help firefighters tackle blazes more safely and effectively, so they can save more lives and reduce structural and material damage to buildings. Smoke Heat Exhaust Vent systems (SHEVs) are designed to delay or prevent flashover – to slow or stop fire developing to catastrophic levels.
Statistics show that 53% of fire-related fatalities result from people being overcome by smoke or gas, rather than dying from the fire itself. Smoke control systems are life-saving devices – greatly increasing an occupants’ chances of survival in the event of fire by keeping escape routes smoke-free.
The primary objectives of the smoke ventilation system is to protect the staircase and common circulation areas. The performance criteria and the design of the system will therefore vary depending on the layout of the common corridors or lobby of the building. Often a building’s design will determine which ventilation system is most appropriate, with British Standard guidance varying depending on a building’s height and the distance from the furthest apartment entrance door to the nearest escape route. Where appropriate the system selected can be driven by design aspirations, space constraints or architectural restrictions.
Mechanical ventilation systems, in particular, provide exceptionally effective smoke control, as well as greater building design flexibility.
Mechanical smoke ventilation systems are comprised of an extract shaft serving common corridors and lobby areas of a building. When smoke is detected within an area covered by the system, the vent to the smoke shaft on the floor where the fire is located will open (all other vents must remain shut). At the same time, the head of stair vent will open to provide make-up air for the smoke extraction system. The fan at the top of the mechanical smoke shaft extracts the smoke and
prevents migration of smoke into the adjacent compartments. The alternative to mechanical ventilation is a natural smoke ventilation system, which opens air ways, and uses natural air-flow dynamics to remove smoke, when a fire occurs.
All SHEV products must pass stringent tests carried out by a fully independent test laboratory and bear the compulsory CE mark. They should also be designed and manufactured to ISO 9001 and meet the requirements of Building Regulations ADB and ADL. Full specification details should be outlined in supporting materials and declaration of performance documents.
We understand the complexities of design and specification of building smoke control. It can be difficult to keep up to date with ever changing products and constantly evolving standards and regulations. With this in mind, we have developed our CPD seminars to provide you with the thorough knowledge you need – book our smoke control CPD, ‘No Fire without Smoke’.
Announcing the launch of our configurator and portal
We’re delighted to announce the launch of our online portal and product configurator tool. At Whitesales, we understood that the process of ordering products could be very complex due to the number of options available to select. We developed unique assembly part codes for our key products and designed the configurator to enable users to quickly and easily generate the correct assembly part code for their required product. Using assembly part codes ensures accuracy when ordering for merchants and customers alike.
The cutting-edge configurator ‘builds’ the product specification as the user selects options through a maximum of 7 steps. The configurator then generates a unique ‘assembly part code’ that is used for ordering.
No more measurement mix ups – just fast, accurate orders every time. The brand new specifier from Whitesales, ask your merchant for details now!
Opening hours & last dispatch date for December 2017
20th Dec: Open (Last normal dispatch date for all products)
21st Dec: Open (Limited dispatch)
22nd Dec: Open until 1200 noon (no dispatch)
25th Dec: Closed
26th Dec: Closed
27th Dec: Closed
28th Dec: Closed
29th Dec: Closed
1st Jan: Closed
2nd Jan: Closed
3rd Jan: Open from 0700 (normal dispatch for all products)
How to build safer buildings with faster, practical completion
Too many construction projects fail to include fire safety management at the earliest planning stages. Yet when you do, you’ll save money, time and be more likely to save lives should fire break out.
Many building designers of big builds and refurbishments lack specific smoke ventilation expertise. Perhaps because it’s only required in buildings of particular size and use, smoke ventilation is often poorly designed or missed out altogether.
Sometimes these requirements are only considered after planning, when building regulations are consulted. By this point it’s difficult to integrate the most effective solution. This results is compromise and more expensive solutions. Is ‘compromise’ a description you ever want to hear about fire safety? Too little knowledge can backfire.
Where there is no specific smoke ventilation expertise, the responsibility gets passed on to fire engineers, who then have very little latitude to create a compliant building. Sometimes smoke vent specialists are only brought in late in design, or even once the building is under construction. This sort of timing is likely to end in more expensive and convoluted bespoke smoke vent design and manufacture.
As a rule, the more complex the building, the more in-depth the knowledge of regulations and British standards you need. Mixed or multi-use buildings may be particularly demanding. Combinations of shops, offices and living accommodation require a solution that addresses all the risks of high fuel loads, large open spaces and 24-hour occupancy. Likewise, many older buildings have severe restrictions on space for modern smoke control and their existing systems are likely to be non-compliant. In such situations, roofs, walls and floors often need to be altered and new fire-proof compartmentation installing.
Yet despite the inherent complications and specialist knowledge required in these more challenging buildings, an all-party meeting – on site and ahead of design – is rare. Perhaps it’s due to the time pressures of modern build programmes. Or perhaps it’s down to assumptions being made.
Things you need not to assume
Sometimes it’s the simple things that are most problematic, often arising from lack of smoke ventilation product knowledge. Examples include: when the angle of opening for smoke vents clashes with other structures; thinking that any control can interface with other building systems, such as BMS and door entry controls; and, most dangerous of all, that all equipment provided under the title of ‘smoke vent’ will be compliant.
It’s a matter of serious concern that there’s rarely a request for documentation or proof of certification. SHEV smoke vents are covered by a harmonised European Standard (hEN) and must be certified to BS EN12101-2). Receiving certification is surely the most fundamental of requirements, especially for a lifesaving device.
All too often, the smoke vent package is split into smaller parts and divided between the façade installation and M&E packages. Or it’s included within the electrical package. In the first situation – without extremely close coordination – the outcome can include ventilation and control compatibility issues, resulting in a non-compliant design. Handing over smoke ventilation to electrical subcontractors should only happen if they are smoke vent specialists. If they’re not, they’ll often have little or no knowledge of the basic requirements of smoke control. That can lead to frantic last-minute rectification and alteration to gain practical completion (PC) of the building. PC is an important date in the schedule and, while different schemes have different interpretations for PC, a working and commissioned smoke control system is non-negotiable.
Where a fire-engineered solution has been commissioned, smoke control, fire strategy documents and drawings tend to be accurate and clear. Without these, smoke control seems to take second place to other design requirements. A lack of joined-up thinking ensues, with inaccuracies around structural apertures, misaligned ducts and more. The inevitable result is reworking and alteration on-site. It’s a needless expense and additional time pressure.
Planning for a better, safer building
The reality is that there’s no ‘one size fits all’ template for a building. Nor is there for smoke control design. Building regulations may be open to interpretation and this can skew priorities. But when you assemble a team of specialists with mutual respect and bring them together before planning begins, you can easily sidestep the pitfalls.
What’s more, you’ll find additional benefits. A carefully designed NSHEV system, for instance, can add comfort cooling and daylight ingress. That means you’ll find it easier to comply with Approved Documents B and F with very little additional equipment and installation cost.
If a solution is designed at an early stage, adopted by the design team and detailed into all drawing issues, showing size, location, power requirements and interfaces, you stand to save hundreds of hours, thousands of pounds, and end up with a better designed, safer building.
Thought leadership: CO2 air quality
How to ensure your building doesn’t undermine your organisation’s performance
It’s not just London’s roadsides where air quality is a cause for concern; indoor air quality in all sorts of buildings is compromising people’s performance and productivity and, in extreme cases, perhaps undermining the very purpose of the building. And all that we’re doing to create this problem is breathing out.
Outside, where the air is clear, we breathe in carbon dioxide (CO2) at a concentration of around 400ppm (parts per million). That’s not even the way nature intended; until the industrial revolution, CO2 averaged no more than 280ppm.* The air we breathe out carries CO2 at 30,000ppm. Outside, that’s rapidly diluted; indoors in a restricted space, we begin to change the composition of the air and increase the CO2 concentration.
All this exhalation is bad for your health if your indoor air isn’t replenished with fresh air regularly. Here are some symptoms you may well recognise, and the CO2 concentration levels at which they’ll start occurring:
|400ppm||Typical outdoor air – ideal for clear thinking|
|600-1,000ppm||Starting to notice a little stiffness and even bad smell|
|1,000ppm+||Drowsiness, feeling tired, yawning – and a drop in decision-making and information-processing performance|
|2,500ppm||Significant drop in decision-making performance|
|20-30,000ppm||Nausea, light-headedness, increased heart rate and breathing|
|50,000ppm||Continuing symptoms, headaches and impaired vision|
Indoors, the act of breathing has a cumulative effect on CO2 concentrations, unless that room is ventilated. In a 14m2 office with just one person, CO2 levels can exceed 1,000ppm in 45 minutes. So it makes sense that if you have 20 schoolchildren and a teacher in a classroom for an hour’s lesson, the CO2 levels are going to increase rapidly. The same principle applies to anywhere where people gather indoors: office buildings, hospitals; even your gym. Without good ventilation, CO2 levels will rise throughout the day.
And what’s the real effect of this unnatural air composition? Even with slightly raised CO2 levels children are feeling a little dozy, pay less attention and take in less information. The teacher might be that bit less logical in explaining an important principle. Cumulatively, since that’s the nature of CO2 and we spend up to 90% of our lives indoors and 50% of that time in the workplace or schoolroom, that could mean lower levels of understanding across all subjects and lower levels of attainment.
It’s early yet to tell exactly how we’re affected in the real world, but some studies have revealed results of real concern. A 2015 study in America conducted by a team from Harvard, SUNY Upstate Medical School and Syracuse University involved a controlled office experiment. Manipulating CO2levels from 550ppm to 1,400ppm and having the participants undertake a Strategic Management Simulation test each day at 3pm. At 945ppm, cognitive functions dropped by 15%. At 1,400ppm, the scores plummeted to 50% lower than on the 550ppm days. The results echo a 2012 study (Satish, Fisk et al), which found that at 2,500ppm some performance metrics fell to levels associated with dysfunctional performance.
If learning, teaching and decision-making might be so badly affected by poor air quality, imagine what might happen in a hospital if CO2 levels are unmonitored and uncontrolled.
Creating an internal climate that works
As the damage of climate change becomes clearer, our industry has worked hard to reduce carbon emissions, tighten building envelopes and provide better insulation. The by-product in many buildings has been that CO2 builds up within.
HVAC systems aren’t necessarily helping; in many cases they recirculate a lot of indoor air to manage temperature levels and reduce energy costs. And if we’re largely recirculating CO2-rich air, we’re also not clearing out any pollutants emitted from building materials, furniture and carpets.
The answer lies in real-time CO2 monitoring linked with opening rooflights or rooflights featuring ventilation systems. When concentration reaches a predetermined level, the rooflights are triggered into action, drawing in fresh air and expelling stale, CO2-laden air. It’s even possible to track levels across different parts of a building when the CO2 sensors feed the building management system. That the rooflights also draw in natural light – with all its proven benefits for everything from improved performance to faster post-op recovery rates to reduced absenteeism – should be an? added incentive.
Test the air in your building at 9am and then at several intervals throughout the day. Track the changes in carbon dioxide. Perhaps monitoring this one performance metric could lead to an improvement in all the others.
* Climate Change: What Everyone Needs to Know, Joseph Romm, OUP, 2015