An Overview of Smoke Detectors

By Samudrapom DamReviewed by Susha Cheriyedath, M.Sc.Updated on Nov 13 2024

Smoke detectors are vital safety devices designed to detect smoke early, alerting building occupants with an audible or visual alarm. By identifying the presence of smoke, often a sign of fire, these detectors play a crucial role in enabling timely, life-saving interventions.^1,2

Image Credits: nikkytok/shutterstock.com

The device features an electromechanical smoke sensor, the core smoke detector, as well as a microcontroller that acts as an audio frequency oscillator to trigger an alarm through a buzzer. Smoke detection is achieved through either physical ionization, optical/photoelectric sensing, or a combination of both methods using dual sensors.^1,2

Types of Smoke Detectors

Photoelectric Smoke Detectors

A photoelectric smoke detector uses a light beam and electrical photocells (photodiodes) to track smoke particles. The light beam (made of an incandescent bulb or infrared LED light that helps to collect the light source into a beam) in the smoke detector will reflect onto the photocells. The photocells are arranged at a right angle to the blight beam so that light entering the chamber does not typically attract the photocells.

When smoke particles enter the optical chamber, these particles interfere with the light beam (i.e., the light reflects off of the smoke particles) and then make contact with the electrical photocells. This contact increases the electrical charge in the detector to a threshold level, which initiates an alarm signal.

Photoelectric smoke detectors are typically installed in large commercial and social settings, including gymnasiums and auditoriums.

Advantages

• Ideal for detecting dense smoke.
• Less prone to false alarms from cooking fumes or shower steam.
• Do not contain radioactive materials, making them safer for use.

Disadvantages

• Sensitive to dust particles and insects, meaning that regular maintenance is needed.
• Expensive to maintain.
• Require more current to operate (they are typically wired to a 110-volt power source).

Ionizing Smoke Detector

Ionizing smoke detectors use radioisotopes, such as americium-241, which ionize smoke particles in the air. The functionality principle of the radioactive isotope americium-241 involves the emission of alpha particles, which ionize air particles in the sensing chamber so that they conduct electricity.

During the emission of alpha particles into the air, a chemical reaction occurs where air molecules in the collecting chamber are ionized and, as a result, carry an electrical charge. Smoke particles surrounding the ionizing smoke detector enter the collecting chamber and attach to the ions, making it more difficult for the ions to deliver an electrical charge.

A circuit detects a decrease in the electrical flow, which triggers an alarm system. This type of smoke detector is ideal for detecting invisible particles produced by fires. It will work much faster and be more sensitive than a photoelectric detector.

Alpha particles are used for the ionizing smoke detector as they have high ionizing potential. Although there are concerns that this type of smoke detector emits radiation, the alpha particles used have low penetrative potential and so will not pass through plastic material.

The standard amount of americium-241 used in the ionizing smoke detector is not enough to raise regulatory concerns – a standard amount of radioactive americium-241 is made up of 37KBq or 1ìCi, which is enough to detect smoke particles without contaminating the outer surface of the detector.

Prior to being sold on the market, ionizing smoke detectors go through a radiation safety analysis to meet safety requirements. Compared to photoelectric smoke detectors, the ionizing smoke sensor is less expensive and more commonly used.

Advantages

• Cheaper than photoelectric smoke sensors.
• Ionizing smoke alarms outperform photoelectric smoke alarms when detecting fast flaming fires with little visible smoke.

Disadvantages

• Highly sensitive, which can lead to false alarms as a product of cooking.
• Not as responsive to smoldering fires; they are slower than photoelectric sensors in detecting smoke particles from smoldering fires.
• The use of radioactive material is a concern.

Dual-sensor Smoke Detectors

Dual-sensor smoke detectors combine both ionization and photoelectric technologies. These dual-sensor detectors aim to provide a more comprehensive detection, improving flaming and smoldering fire response times.^2,3

These detectors minimize the chances of false alarms through more precise detection of different types of fires. Thus, dual sensor detectors are often recommended for installation in buildings as they provide crucial time for occupants to respond in case of fires.^2,3

Advantages

• Faster response.
• Enhanced fire detection.^2,3

Disadvantages

• Typically more expensive than single-sensor technologies.
• Greater complexity due to the incorporation of two technologies.^2,3

Smart Smoke Detectors

A smart smoke detector is an advanced version of a conventional smoke detector that is connected to a home/building's Wi-Fi network/smart home system. These detectors not only detect smoke and sound an alarm, but also send notifications to smartphones, tablets, or other connected devices when smoke is detected, allowing for remote response and monitoring.⁴

Typically, components like microcontrollers, smoke sensors, buzzers, complete Wi-Fi networking solutions, and light-emitting diodes are used in smart smoke detectors. In some advanced models, other sensors like heat and humidity sensors are also included in the design to reduce false alarms.⁴

Advantages

• Remote alerts.
• Enhanced detection due to the use of additional sensors.
• Integration with smart home systems.⁴

Disadvantages

• Reliant on a strong Wi-Fi connection.
• HIghly complex.
• Data privacy and security concerns.⁴

Recent Advances and Future Trends

Improving early fire detection while keeping false alarms to a minimum is a big challenge. Recent advancements are tackling this by using Mie scattering theory, which studies how light interacts with particles. Scientists discovered that by comparing how two different wavelengths of light scatter off particles, they can better identify the unique properties of smoke.⁵

One recent innovation published in Fire introduced a dual-wavelength smoke detector that measures both scattered light and light extinction. This design can reliably differentiate between real fires and common false alarm triggers without complex calculations. Tests with real fires (meeting European Standard EN 54) and computer simulations showed that this new detector has real potential to make smoke monitoring more accurate and dependable.⁵

Artificial intelligence is also making waves in smoke detection. Researchers are exploring the use of artificial neural networks (ANNs) to help smoke detectors distinguish real fire smoke from other particles, like steam or dust. With ANNs, smoke detectors could become more accurate, reducing the chances of false alarms and making buildings safer.⁶

Key Market Players

Honeywell International Inc., Johnson Controls, and Hochiki America Corporation are some of the prominent players dominating the smoke detector market. They offer a range of products for residential and commercial applications, providing early warning in case of fires and enhancing safety.

Honeywell is known for its reliable fire safety solutions, including smoke detectors with ionization and photoelectric technologies, often featuring smart home integration and real-time monitoring. Johnson Controls specializes in innovative fire detection systems that emphasize advanced technologies like wireless connectivity. Hochiki Corporation, a leading manufacturer from Japan, provides a variety of smoke detection products, including automatic fire alarms with advanced optical sensing technology for quick response.

Other notable companies in the market include Carrier Global Corporation, Siemens AG, ABB Group, Schneider Electric, Robert Bosch Stiftung, and Resideo, all of which are committed to continuous innovation and expanding their offerings to enhance safety and reliability.

Conclusion

Smoke detectors are essential for safety, and recent advancements are making them even more effective at early fire detection. With innovations like dual-sensor technology, AI, and smart connectivity, today’s smoke detectors are not only reducing false alarms but also enhancing reliability and convenience.

Leading companies like Honeywell and Johnson Controls continue to push the boundaries of fire safety technology. As these advancements unfold, we can expect even safer homes and workplaces, protected by smarter, more responsive smoke detection systems that offer peace of mind for the future.

References and Further Reading

1. Ogunbor, S. E., Akperegi, C. (2020). Design and Analysis of Smoke Detector System. https://www.researchgate.net/publication/360472928_DESIGN_AND_ANALYSIS_OF_SMOKE_DETECTOR_SYSTEM
2. How Do Smoke Detectors Work? [Online] Available at https://www.nist.gov/how-do-you-measure-it/how-do-smoke-detectors-work (Accessed on 13 November 2024)
3. Khan, F., Xu, Z., Sun, J., Khan, F. M., Ahmed, A., & Zhao, Y. (2022). Recent Advances in Sensors for Fire Detection. Sensors, 22(9), 3310. DOI: 10.3390/s22093310, https://www.mdpi.com/1424-8220/22/9/3310
4. Adenan, M. S. M., Erwan, A. N. M., & Alfian, M. N. H. M. (2021). Smart Smoke Detector. International Journal of Recent Technology and Applied Science (IJORTAS), 3(1), 16-31. DOI: 10.36079/lamintang.ijortas-0301.198, https://lamintang.org/journal/index.php/ijortas/article/view/198
5. Li, K. et al. (2023). Dual-Wavelength Smoke Detector Measuring Both Light Scattering and Extinction to Reduce False Alarms. Fire, 6(4), 140. DOI: 10.3390/fire6040140, https://www.mdpi.com/2571-6255/6/4/140
6. Choueiri, S., Daoud, D., Harb, S., & Achkar, R. (2020). Fire and Smoke Detection Using Artificial Neural Networks. 2020 14th International Conference on Open Source Systems and Technologies (ICOSST), 1-6. DOI: 10.1109/ICOSST51357.2020.9332990 , https://ieeexplore.ieee.org/abstract/document/9332990
7. Ionization vs. Photoelectric Smoke Alarms [Online] Available at http://www.structuretech1.com/2012/04/ionization-smoke-alarms/

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