NAP-07 Ion Chamber Smoke Sensor

This is an ionization smoke detector which uses a radioisotope, typically americium-241, to ionize air; a difference due to smoke is detected and an alarm is generated. Ionization detectors are more sensitive to the flaming stage of fires than optical detectors, while optical detectors are more sensitive to fires in the early smouldering stage. The smoke detector has two ionization chambers, one open to the air, and a reference chamber which does not allow the entry of particles. The radioactive source emits alpha particles into both chambers, which ionizes some air molecules. There is a potential difference (voltage) between pairs of electrodes in the chambers; the electrical charge on the ions allows an electric current to flow. If any smoke particles enter the open chamber, some of the ions will attach to the particles and not be available to carry the current in that chamber. An electronic circuit detects that a current difference has developed between the open and sealed chambers, and sounds the alarm.

Technical Specification

• Diameter: 37mm
• Ionization source characteristics and radiation safety performance:
• The ionization chamber fitted with a high performance and low activity of Am-241 ionization
• Ionization source activity: 0. 5uCi ( 18KBq . 0. 8uCi±10% ( 30KBq±10% )
• Ionization source a spectroscopy: peak: 4. 5MeV ± 10%, FW HM<0. 7MeV
• Safety grading standards ( GB4075, IS02919 . C64444
• Ionization chamber radiation dose rate at 25cm: 0. 03mGy/ ( 1mGy value lower than population dose standard )
• Conditions: outer electrode and the source electrode voltage ( VDD supply voltage ): 9V
• Environment temperature: 20 + C: close to atmospheric pressure standard atmospheric pressure, clean air
• Collecting electrode equilibrium potential: 5. 3~6. 5V
• Collecting electrode potential with the smoke concentration change
• Light reduction rate was 1% feet: 0. 6V
• Light reduction rate was 4% feet: 2. 2V
• Insulator leakage current ( Max ): 0. 5Pa
• Capacitor ( collection of extreme outer electrode + to the source base ): 6. 0pF