When it comes to detecting smoke, time is of the essence. That is why we designed a test that simulates a real-life emergency. 

The first thing to know is that there are two main types of fires that these products are designed for: smoldering fires and flaming fires.

A smoldering (or slow-burning) fire refers to the combustion that occurs at the surface of a solid material. Smoldering fires produce large amounts of thick smoke but can’t sustain a flame. Think of a cigarette slowly burning but never actually bursting into flames. 

CNET's smoke detector test chamber sits outside atop a cast-iron chimney, with flames flickering in the oven below.

Smoke detection testing in progress.

Gianmarco Chumbe/CNET

A smoldering fire can and will become a flaming fire if proper action is not taken immediately.

Flaming fires are the ones we’re more familiar with, and they usually arise from the ignition of any flammable material, such as a flammable substance, wood, paper, etc. These generally produce less smoke than a smoldering fire but are obviously more destructive.

We built a chamber that houses the smoke detector under test and fed to it the two different types of smoke through a chimney. Then, we timed the quickness of the response. The faster the smoke detectors’ alarm was triggered, the better.

To simulate smoke coming from a smoldering fire, I ignited 300g of charcoal and let it heat up for 10 minutes before feeding the smoke. I wanted to make sure most of the coals were ignited and that the smoke was thick enough to trigger the alarm. 

Recreating a flaming fire was easy, just 30g of shredded paper did the trick. Again, I ensured a significant amount of smoke was present before feeding it through the chimney and into the chamber. 

To the great discomfort of my neighbors, who had to endure smoke alarms going off randomly, and to whom I sincerely apologize, I repeated the whole process three times per smoke detector model under test and per type of smoke, totaling six test runs per smoke detector. Finally, I averaged the response times. You can check them out in the chart below: