Catalytic bead sensors are used primarily to detect combustible gases. They have been in use for more than 50 years. Initially, these sensors were used for monitoring gas in coal mines, where they replaced canaries that had been used for a long period of time.
The sensor itself is quite simple in design and is easy to manufacture. In its simplest form, as used in the original design, it was comprised of a single platinum wire. Catalytic bead sensors were produced all over the world by a large number of different manufacturers, but the performance and reliability of these sensors varied widely among these various manufacturers.