Smoke Detectors

Acclimate™ Multi-Criteria Detector

The Acclimate 2251TMB photoelectric detector includes thermal detection at 135°F. It uses advanced onboard software to combine the signals from the photo and thermal elements to create a true multi-criteria detector that responds quickly to real fires while rejecting nuisance alarms.

The Acclimate detector can also adjust its sensitivity according to its environment. Using advanced software, Acclimate continuously samples the air in the environment and adjusts its detection parameters and alarm threshold accordingly. It does this automatically without user intervention. There’s no need for an installer to set sensitivity levels at the control panel – Acclimate makes the educated decisions. In fact, Acclimate has proven its effectiveness and reliability in over one million installations.

For more information on Acclimate and other multi-criteria detectors, visit




i3 Smoke Detectors

i3 Series Smoke Detectors deliver intelligence, installation ease, and instant inspection for optimal performance and reduced costs. A plug-in design and Stop-Drop ‘N Lock™ mounting simplify installation. Smoothing algorithms and intelligent drift compensation minimize nuisance alarms. Accessories for remote sensitivity testing and remote maintenance signaling enable instant inspection.

i3 Series detectors come in multiple configurations to match a variety of application requirements. Standard i3 conventional photoelectric detectors meet most application needs, including those for office buildings, retail establishments, hotels, and residences.

Two- and four-wire Auxiliary Form C Relay detectors are ideal when controlling auxiliary functions, such as elevator recall or door closure, is required.

Sounder models are ideal for residential applications. These two- and four-wire units generate an 85 dBA temporal tone and can easily be synchronized with the i3 reversing relay/synchronization module.

The four-wire Isolated Thermal model initiates a local alarm when smoke is detected and a general alarm when the thermal sensor is activated. These are well-suited for applications like dormitories, retirement facilities, and lofts.

For more information on i3 series smoke detectors, visit


Are You Ready for the Next Evolution of Fire Detection?

Are You Ready for the Next Evolution of Fire Detection?

Next Evolution Products:
Advanced Multi-Criteria Fire Detector and CO1224T CO Detector

Fire research from the 1970s remains relevant today in understanding how smoke detection saves lives. Based in part on research updates and findings, new technology offers the industry’s most advanced detection and protection ever.

Where there’s fire, there’s smoke. According to the Centers for Disease Control and Prevention, more fire victims die from smoke and toxic gases than from burns.

There’s no doubt that smoke detectors save lives. But that’s a fact that we take for granted. Residential smoke detection installations rose astronomically following pivotal research conducted in the 1970s. This research provided a key understanding of how smoke detectors save lives in real-life scenarios. Although residential conditions have changed significantly since then, many of the findings from this period have remained relevant. This research, and an updated version of it, is shaping the new generation of detection technologies.

Clarifying Smoke

The Detector Sensitivity and Siting Requirements for Dwellings, known as the Indiana Dunes (Dunes I) research study, is still a benchmark for research. The study was conducted from 1974 to 1976 for the National Institute of Standards and Technology (NIST), formerly the National Bureau of Standards, under contract with the Illinois Institute of Technology Research Institute and Underwriters Laboratories (UL). It focused on the placement and sensitivity requirements of smoke detectors in residential homes that were scheduled for demolition as part of an expansion of the Indiana Dunes National Lakeshore Park.

Researchers selected readily available detectors and installed them in homes to measure their performance during a fire. Residences with contents manufactured in the 1960s and early 1970s were set afire and used as test beds. Each of the test rooms was instrumented so that conditions such as temperature and smoke obscuration were continually monitored. Test fires were ignited to judge when unassisted escape to safety (but not jumping out windows) would no longer be practical.

The report presented results in a unique way. It defined adequate lifesaving potential by the amount of time people in a household would need to escape using the “primary escape path,” which was defined as the path from any room to one of the exterior doors. The escape time was measured from the time when the detector went into alarm until a room’s condition reached one of the defined tenability limits (e.g., smoke optical density, temperature, or CO concentration). This was the first test that evaluated detection performance based on the amount of escape time that started upon detector actuation. These escape times populated a probability plot showing the percent of experiments that met or exceeded specific minimum escape times. Results for safe escapes were determined by selecting a minimum escape time and then selecting the percent of cases in which that time was available. Based on the test results, smoke detection on every level of a home provided adequate escape time in approximately 90% of the fires.

Installing smoke detectors on every floor level of the home yields optimum performance because it is impossible to predict where a fire might start. The closer a smoke detector is to the fire, the faster it will respond, allowing more time for residents to escape. For example, walls, stairs and HVAC systems, especially air conditioning, can impede smoke propagation to a detector. Therefore, coverage on all levels is imperative.

The results of the Dunes I test established the sensitivity limits for the Single and Multiple Station Smoke Alarms standard UL 217, utilized for residential applications. The same smoke obscuration limits of 0.5% to 10% were subsequently adopted into Smoke Detectors for Fire Alarm Signaling Systems standard UL 268, applicable to commercial buildings.


Duct Smoke Detectors — Frequently Asked Questions

A primer on selection, installation and testing.
Duct Smoke Detectors
Which type of duct smoke detector is preferred for HVAC applications, photoelectric or ionization?

Photoelectric detection is preferred for several reasons, including:

1. Detection Capability — Photoelectric detection responds better to the larger smoke particles found in ductwork during a fire.
2. NFPA Recommends Photoelectric — The National Fire Alarm Code Standard 72, section A. explicitly states, “In almost every fire scenario in an air-handling system, the point of detection will be some distance from the fire source, therefore, the smoke will be cooler and more visible because of the growth of sub-micron particles into larger particles due to agglomeration and recombination. For these reasons, photoelectric detection technology has advantages over ionization detection technology in air duct system applications.”
3. Environmental Immunity — High humidity and condensation can cause false alarms with ionization detectors. Photoelectric detectors operate more efficiently, generating fewer false alarms.
4. Industry Preferred — Photoelectric detection is preferred by the fire alarm industry, manufacturers of commercial packaged air conditioning units and major retailers.
5. Low-Flow — Photoelectric detectors are capable of operating in air speeds as low as 100 feet-per-minute to meet new HVAC applications and codes with variable air volume systems and fire smoke dampers.

best procedure for testing System Sensor duct-mounted smoke detectorsWhat is the best procedure for testing duct-mounted smoke detectors?

There are four simple steps to test duct-mounted smoke detectors:

1. Verify the detector is installed per NFPA 72 guidelines and is in accordance with the manufacturer’s installation instructions.
2. Employ the detector’s built-in test feature, such as the test magnet or accessory test switch. These features are designed to meet NFPA and Underwriters Laboratories functional test requirements that ensure the detectors are operable and will respond to minimum smoke requirements.
3. Measure the pressure differential across the sampling tubes (exhaust and intake) with a manometer to ensure the detector will respond to smoke in the duct airflow. This is the manufacturer’s acceptable test.
4. Apply smoke directly to the detector head to initiate an alarm. The sampling tubes may need to be blocked off for this test and then reopened afterwards.

Why is a smoke bomb test not recommended for ionization duct smoke detectors?

Based on evidence with in-house and field-testing of ionization, duct-mounted smoke detectors, there are three notable reasons:

1. Ionization smoke detectors are most sensitive to smoke particles ranging from .01 to .3 microns. Particles produced by smoke bombs tend to become larger the farther they travel from the source, triggering a slow response.
2. Smoke bombs produce cold smoke particles, which are larger and not as easily detected by ionization smoke detectors. These particles are also dependent on relative humidity, distance traveled from the source and time of activation. This phenomenon is caused because the smoke is more of a mist than suspended solids in warm gases. In other words, the smoke doesn’t represent a true smoke composition or fire signature for smoke detector activation.
3. It is possible to pass a smoke bomb test, but to be out of the required manometer range for sampling, giving the installer a false sense of proper operation.

Although unadvisable, if you choose to conduct a smoke bomb test, use a photoelectric smoke detector, which typically responds to smoke particles between .3 and 10 microns, and, if you have a respiratory ailment, use a self-contained breathing apparatus.

Where can a duct-mounted smoke detector be installed in relation to the duct?

Duct-mounted detectors can be installed horizontally and vertically to - and on top of, within and underneath - the duct. However, we do not recommend installing underneath the duct because condensation may drain into the electronic circuitry and cause electrical damage.

To determine the best location, we recommend comparing the pressure differential between the sampling and exhaust tube. The pressure differential must be within specified limits of .0015 to 1.20 inches/water for photoelectric smoke detectors. The detector housing cover must be securely fastened to complete the airtight enclosure for proper air sampling and to restrict contaminants from entering the detector head.

In order to shut down the HVAC system, what do I connect my HVAC or RTU (Roof Top Unit) to?

To provide immediate shutdown during an alarm, connect to the controller voltage from the RTU. Connecting to the thermostat will only allow a gradual shutdown of the HVAC system. In some cases, the RTU manufacturer requires a shutdown of this type because, if stopped too fast, the bearings could become damaged. Be sure to review each situation accurately.

Can any test station and other accessories be used with any duct smoke detector manufacture?
SSK451No. Duct detectors, test stations, and other accessories manufactured by different companies are not compatible with each other due to a different electrical makeup.


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