Building smoke detectors is an art – and Walter Vollenweider (58) is a master of the craft. Vollenweider has been continually improving the design and technology of these devices for around five years now. Among other things, his inventions have reduced false alarms and lowered production costs through the implementation of new manufacturing techniques.

Vollenweider, who currently works as a Senior Development Engineer at Siemens Building Technologies in Switzerland, is constantly coming up with new ways to improve optical smoke detectors. The principle behind the way these devices function is actually quite simple: Two light-emitting diodes project light into the interior of an optical measuring chamber — a type of labyrinth with plastic walls that guide the light from the two sources into precisely defined paths. These light beams are partially scattered backward if they hit smoke particles in the air. A built-in photo cell absorbs the scattered light, measures its intensity, and issues a command to sound an alarm if necessary. Other types of suspended matter also enter the detector, however, and the system has to distinguish between these and smoke particles. “Insects are generally too big to be confused with smoke particles,” says Vollenweider, “but dust and steam can cause a mix-up and therefore present us with a big challenge.” The problem can be solved by analyzing the scattered light over time. Every few seconds, the system processor analyzes new data and compares it with predefined patterns. If after a certain number of measurements the substances in question continue to resemble smoke particles, an alarm is triggered.

“Our goal is to reduce false alarms to a minimum,” Vollenweider explains. This is something of a fine art, especially when you’re working with open smoke detectors, as these don’t have the labyrinth inside their housings. Instead, the devices illuminate the particles to be detected outside the casing and then measure and evaluate the light reflected by these particles.

Vollenweider views himself as a development realist who takes production costs into account as well. After all, large buildings like skyscrapers need to be equipped with thousands of smoke alarms, so unit prices should be as low as possible. “That’s also why you can’t use risky optical arrangements that can only be assembled by hand,” Vollenweider explains.

The inventor studied electrical engineering at the Swiss Federal Institute of Technology (ETH) in Zurich before beginning his career in the area of communications engineering 35 years ago. He turned his attention to smoke detectors five years ago, and since that time he and his colleagues have registered many patents. Vollenweider is also considered to be the development team’s specialist when it comes to aesthetic solutions. “Smoke alarms protect buildings, but that doesn’t mean they should spoil the way a building looks,” he says. “In particular, they should be as inconspicuous as possible in places like museums, elegant reception halls, and historical buildings.” If you put all of Vollenweider’s inventions together, beginning with communications technology, the sum total is 23 inventions, 80 individual patents granted, and 26 patent families.

Vollenweider doesn’t just enjoy experimenting on the job, though: “I’m pretty adventurous as a cook,” he says. “But I tend to avoid recipes.” In fact, he doesn’t even bother to document the results of his culinary experiments. “The problem is that when something turns out real good, I can never exactly reproduce it.”