Photoelectric detectors will have a light sensor (usually a small, round object) visible inside the chamber, while ionization detectors will not.
Determining which type of smoke alarm you currently have can be difficult. If you find anything mentioning radioactive materials, a model number with an “I” or any mention of Americium-241 on the alarm's label, it is an ionization alarm. If you find a “P,” it is a photoelectric alarm.
You can do so by taking the smoke alarm down and look at the back for either “Photoelectric” or “Ionization,” or a symbol with the letter “P” or “I” on the back. Once you figure out which type you own, purchase the other type and install one next to each unit.
There are some different types of alarms that can be purchased that have different pros and cons. Most often, you will see information pertaining to photoelectric vs ionization alarms. The difference between these two types is the sensor that is used to detect the smoke.
In controlled experiments, ionization alarms react earlier than photoelectric alarms in fast-flaming fires, such as those involving paper or flammable liquids, while photoelectric alarms tend to react substantially earlier than ionization alarms in smoldering fires, such as those ignited by cigarettes in upholstered ...
This is why the National Fire Protection Association recommends the use of both ionization and photoelectric technologies in all smoke detectors. NFPA 72 advises having both photoelectric and ionization alarms for optimal protection against different types of fires.
Potential for False Positives in Dusty Environments
While photoelectric detectors are generally less prone to false alarms, they can still be triggered in dusty environments. Particulate matter in the air, such as dust or insect debris, may scatter light and lead to false positives.
Kidde offers photoelectric and ionization smoke alarms as well as a dual-sensor alarm that combines both technologies in one unit. All three can be found at home improvement stores and other retailers nationwide, or online.
Photoelectric Smoke Alarms
These alarms detect visible particles of combustion, which is why it's often said that they “see” smoke. They work by aiming a light source into a sensing chamber so that when smoke particles enter the chamber, light is reflected onto the sensor and triggers the alarm.
Many fire safety websites state that photoelectric smoke alarms are less prone to nuisance alarms in the kitchen area than ionization smoke alarms, and also include other options or qualifying comments. One manufacturer has conducted tests at corporate research facilities.
To find the model number or date of manufacture for your alarm, disconnect your alarm from power and remove it from the wall or ceiling. Valuable information about the alarm is printed on the back of the unit.
How to Tell If Your Smoke Alarm is Working. Hardwired units will have a steady green LED light to show that it's receiving AC power. Battery-operated units will have a quick flash every 30-45 seconds. This does not necessarily mean the alarm is working.
Can I install a hardwired smoke detector myself? While it is technically possible, it is not recommended. Working with your home's electrical system can be dangerous and complex, best left to a qualified electrician.
Test smoke alarms every month by pressing their test buttons. If your alarms use regular batteries, swap in fresh batteries at least once a year. A “chirping” sound means that it's time to change batteries. Because alarm sensors wear out, replace each alarm at least every 10 years.
Ionization sensing technology is generally more sensitive than photoelectric sensing technology at detecting small particles, which tend to be produced in greater amounts by flaming fires. These types of fires consume combustible materials rapidly and spread quickly.
Photoelectric smoke alarms sound tens of minutes faster than ionization smoke alarms during smoldering stage fires with significantly fewer false alarms. Furthermore, their performance in flaming stage fires is comparable to ionization alarms, making the photoelectric alarm the best choice.
The researchers concluded that ionization smoke alarms were poor at detecting smoke from smoldering fires; that many fires begin as smoldering fires before transitioning into flaming fires; therefore by the time an ionization detector goes into alarm the occupants could already be dead.
What causes false activations of smoke alarms. If hardwired interconnected photoelectric smoke alarms are activating and there is no identifiable cause for the activation (eg. dust), the issue could be related to either the power supply or incorrect installation.
This type of smoke alarm DOES look like your standard smoke alarm, however, you can tell it is a photoelectric smoke alarm if it DOES NOT have a radiation symbol on it. If your smoke alarm carries a radiation symbol it is an ionisation style and should be replaced as soon as possible.
Low battery: This alarm is equipped with a low battery monitor circuit which will cause the alarm to produce a single “chirp” approximately every 60 seconds and blink the Red LED every 30 seconds, for a minimum of seven (7) days should the battery become low.
Kidde Alarms: If you look at the back of the alarm, you will see the name of the product and the model number in bold text below the logo. Firex Alarms: If you look at the back of the alarm, you will see where the text is split into two columns, with text on the left and text on the right.
Like coupons and canned goods, smoke alarms have an expiration date. "They have a life of 10 years," Roux says. "But, if it has a built-in CO detector, you'll need to replace it sooner." According to Consumer Reports, most CO detectors come with a five- to seven-year warranty.
Dense water vapor is like humidity when it comes to triggering false alarms. When you take a shower or boil water on the stove, smoke detectors can sense the steam and sound the alarm. Make sure you ventilate your bathroom and kitchen properly to prevent this.
A disadvantage of the photelectric effect is that it's pretty limited to working with some elements only. Light has a short range in the wavelength spectrum, consisting from 400 - 700 nm. Also, not only wavelength plays a role in the effect, radiation intensity is also considered an important factor.