The changes to these commercial and residential standards were driven in part by two factors occurring in tandem:
- Research into material-burning sponsored by the National Fire Protection Association (NFPA) and others showing that modern buildings typically contain materials and furnishings comprised of synthetic materials, such as polyurethane foam, that are known to ignite and burn faster than traditional materials.
- Excessive nuisance alarms often resulting in disabling of smoke alarms by consumers in residential applications, as well as costly deployment of emergency responder resources. In 2014 alone, according to the NFPA Journal, U.S. fire departments responded to 2.5 million false alarms, twice the number of actual reported fires and five times the number of actual structure fires.
Answering the need for more sophisticated devices, the industry is stepping up to meet these ground-breaking requirements to alarm faster with greater accuracy and avoid alarming for non-events. In essence, new devices will need to be capable of differentiating between truly threatening fast-flaming or smouldering fires and nuisance sources. This is a major advancement for commercial building operators, especially in hospitality, healthcare and other facilities where nuisance alarms frequently occur.
Breaking new ground
The significant revisions to UL 268 incorporate three new test methods, including a new cooking nuisance alarm test and two polyurethane foam tests for smouldering and flaming fires. These new tests better represent the smoke profiles and behaviour of modern building fires to help ensure next-generation sensors are designed to give building occupants enough time to evacuate safely.
Updates to standards can pose a significant challenge to manufacturers, especially when they are as significant as these new fire tests. At Edwards, we knew these changes were forthcoming as we actively participate in several committees that are part of UL’s Collaborative Standards Development System, as well as NFPA committees. These consensus efforts ensure that all voices are heard in arriving at the advances needed.
At its facility outside Chicago where smoke detection research is conducted and products can be tested for listing, UL built a new 800-square-foot lab to deliver controlled, consistent and repeatable measurements in testing. The facility controls climate variables such as humidity, air pressure and thermal equilibrium consistency.
Because of the dual nature of the challenge – responding appropriately to both nuisances on the one hand, and smouldering and flaming polyurethane fires on the other – Edwards’ product engineers were faced with a monumental task in the product design. A new detector couldn’t react to a nuisance too early but still needed to react quickly enough to aggressive fires determined by UL’s flaming polyurethane test fire and it was confirmed that existing sensing technologies would not be able to pass the new tests.
To respond to this daunting task, Edwards made the investment to update our own fire test lab in Bradenton, Florida to replicate the new UL facility. This allowed us to efficiently manage our development efforts by testing our solution in a lab environment before going to UL. The renovations included installing a removable floor to match the volume of the UL official smoke room but still allow flexibility to run EN54 fires as well incorporating space and equipment to pass the cooking nuisance test. Additional reference sensors were added and the room was rewired to enable automated monitoring of test data.
Let there be light
The question then became: What information was needed to better understand how particles and smoke are deciphered inside a photoelectric smoke detector chamber? With photoelectric detectors, particles of smoke scatter light beams to alarm-triggering sensors. It became clear that the detector needed to examine the behaviour of smoke particles to determine more precisely what types of particles were entering the chamber. In this way, it was possible to exclude particles of water vapour, dust or other nuisances from the equation.
As particles enter the chamber of the new sensor, they are analysed to determine if the particles stem from a real fire or a nuisance source. If the microprocessor in the detector senses that there should not be an alarm based on predetermined parameters, no alarm sounds. This innovative approach was quickly matured using advanced design principles and the Edwards state-of-the-art fire test room.
Adding polyurethane detection into the mix brought an entirely new level of complexity into our examination due to the difficulty of sensing the particles. Traditional materials such as wood and cotton burn more slowly, producing more particles, while modern synthetics burn more quickly and generate fewer particles. In the latter instance, other ambient air characteristics can compete with the particles in trying to enter the detector chamber, creating a monitoring challenge. We realized that the key to solving this was identifying more information about the particles entering the chamber through new sensing methodologies in combination with light obscuration.
In the end, Edwards evolved a sophisticated optical detection methodology that balanced cost and performance, and we are very proud to be the first multi-criteria smoke detector manufacturer to receive certification to the UL 268 standard. The new decade will truly bring enhanced protection of people and property, while minimizing false alarms that cause business interruption and unnecessary responses by fire departments.
For more information, go to www.edwardsfiresafety.com/Optica
