Health & safety


terms of obscuration levels (or in some cases both). Obscuration is a unit of measurement for the concentration of smoke. It measures the amount of light that reaches the detector (D) in the presence of smoke compared to the amount of light that reaches the detector (D) in clean air. The higher the value of obscuration, the higher the smoke concentration levels. The most stringent testing standards are


currently NA/Canada UL 217 and UL 268. Some of the relevant tests are listed here, but there are many more:


UL 217 (8th edition)/UL 268 (7th edition)


Figure 3. An ADPD188BI smoke detection module.


Paper Fire ■ Must give an alarm before t = 240 s


Wood Fire ■ Must give an alarm before t = 240 s


Smoldering Smoke ■ Must give an alarm before obscuration levels exceed 29.26%/m


Flaming Polyurethane Foam ■ Must give an alarm before obscuration levels exceed 15.47%/m and t = 360 s


Smoldering Polyurethane ■ Must give an alarm before obscuration levels exceed 34.3%/m


Hamburger (Nuisance Alarm) ■ Must not give an alarm/fault before obscuration levels exceed 0.987%/m or the MIC value is in the 59.3 per cent to 49.2 per cent range


Sensitivity Test, Dust Test, High Humidity Test ■ Must not give an alarm/fault ■ The sensitivity test measures the obscuration level at which the unit alarms in a controlled smoke chamber


Flammable Liquid Fire (UL 268 Canada Only) ■ Must give an alarm before t = 240s


For EN 14604, BS EN 54, and ISO 7240,


there can be different sensitivity levels on the same test or additional specifications per taining to, for example, liquid (heptane) fire, glowing smoldering cotton, or low


40


temperature, black smoke liquid fire. For a complete set of tests, the relevant specification must be referenced in full.


Provisions for TesTing and How inTernaTional regulaTions Can overlaP


The following are the requirements for the five main test regulations:


UL 268 and UL 217 ■ 28 assembled specimens, all of which are used for each test (unless otherwise agreed with the testing agency)


EN 14604 ■ 20 specimens: specimens numbered in order of increasing response threshold (decreasing sensitivity)


BS EN 54 ■ 22 specimens: six least sensitive specimens numbered 17 through 22 and the others arbitrarily numbered 1 through 16


ISO 7240 ■ 20 specimens: four least sensitive specimens numbered 17 through 20 and the others arbitrarily numbered 1 through 16


The test sets are important as they


determine how many detectors are needed for each test within the five standards. UL 268 and UL 217 require 28 specimens, all of which are used for each test. For the other three standards, the specimens are numbered as detailed and specific specimens are then required to pass specific tests. For example, in ISO 7240 all specimens are tested for the reproducibility test, yet only specimen 3 is tested for the dazzling light test. What this means for global compliance is that, because specific devices are required to pass specific tests for compliance, each test in each standard


must be performed and standards cannot be overlapped. In some cases, the testing conditions are identical between the two different UL standards, so compliance with one standard will mean compliance with the other. EN 54-29, EN 14604, and ISO 7240 have


identical requirements for the smoke tunnel and fire room—both of which certain tests are carried out in. The required atmospheric conditions for these standards are also identical. In some cases, the testing conditions are identical between the two different UL standards, so compliance with one standard will mean compliance with the other.


smoke deTeCTion TeCHnology: one size does noT fiT all


This article has summarised some smoke detection technologies, definitions, and smoke detector tests and how they relate to five international standards. It is not meant to be a detailed analysis of one standard over another. Instead, the article uses some examples to show how stringent and complicated the process to meet smoke detection regulations can be. Each international region has a very detailed set of tests that have different methods (and setups) for testing. However, passing UL 217 and UL 268


standards—currently the most stringent pair of standards—can give a good indication of compliance, although this is not a substitute for regional testing. For regional compliance, a very detailed examination of local test requirements and methods is required. Even at local country level, regulations will increasingly become more stringent in the future. Using a component or subsystem that is UL


listed provides ease of mind. UL component recognition means that UL has evaluated components or materials intended for use in a complete product or system. These components are intended only for end-use products that may be eligible for UL certification. The ADPD188BI plus smoke chamber is pending for UL listing as of the publication of this article. The ADPD188BI smoke detection module


January 2021 UKManufacturing


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