Cautions for Use of Gas Sensors
Be sure to read carefully

Ⅰ. Safety Precautions for Use of Figaro Gas Sensors

  • Carefully read product information and other technical information provided by Figaro before using our products, and confirm specifications and operating conditions.
  • When designing an application circuit, please make sure that an accidental short circuit or open circuit of other electronic components would not cause the sensor to be subjected to excessive voltage, current, or temperatures exceeding the rated values.
  • When designing application products, please make sure that a gas sensor malfunction would not
    1) cause adverse effects on other components,
    2) directly or indirectly impair the safety of application products that use gas sensors (e.g., emit smoke, cause fire, or other unstable states of application products).
  • Consider adding safety measures for fail-safe where necessary, such as a protection circuit.

Ⅱ. Cautions for Use of MOS-type Gas Sensors

【Conditions for use and storage】

  1. 1) Rated temperature and humidity conditions
    Using or storing the sensor in an environment outside the rated temperature and humidity range may cause physical damage and/or affect the sensor characteristics.
  2. 2) Storage conditions
    When storing for a long time, store the sensor in a sealed bag whose material does not emit odor or gas. Do not use dehumidifiers such as silica gel in the bag.
  3. 3) Condensation
    If water condenses inside the sensor housing, sensor characteristics may drift.
  4. 4) Freezing
    If water freezes on the sensing element surface, sensor characteristics may drift
  5. 5) Oxygen concentration
    The sensor cannot properly operate in an environment with oxygen content other than normal ambient oxygen concentration.
  6. 6) High concentration of gases
    Sensor performance may be affected if exposed to a high concentration of gases for a long period of time during the operating or storage period.
  7. 7) Organic vapors
    If the sensor is exposed to organic vapors generated from alcohol, acetone, volatile oil etc., organic vapors will adsorb onto the sensing element surface, and sensor performance may be affected.
  8. 8) Dusts and oil mist
    Sensor performance may be affected if exposed where excessive dust, fine particles, or oil mist is present.
  9. 9) Silicone
    Sensor performance may be affected if exposed where silicone rubber/putty, or adhesives or hair grooming materials containing silicone are present. Avoid usage and storage of the sensor where such silicone-containing materials may be used.
  10. 10) Alkaline metals
    Sensor characteristics may be changed if the sensor is contaminated by alkaline metals. Avoid contamination by alkaline metals, especially salt water spray.
  11. 11) High concentration of corrosive gases
    Sensor performance may be affected if exposed to a high concentration of sulfur-based or chlorine-based corrosive gases for extended periods. Avoid usage and storage in highly corrosive environments.
  12. 12) Sensor with filter
    Sensor performance may be affected if the sensor with filter is exposed to organic vapors such as alcohol for extended periods, causing breakthrough of the filter. Avoid usage and storage in such environments.

【 Handling 】

  1. 1) Applied voltage
    If higher than the rated voltage is applied to the sensor circuit or the heater, the sensor may be damaged or sensor characteristics may be irreversibly impaired. Do not use the gas sensor if excessive voltage is applied.
  2. 2) Mechanical shock and vibration
    Avoid mechanical shock. Breakage of lead wires, short-circuit inside the sensor, or change in sensor characteristics may occur if the sensor is subjected to a strong shock or vibration. Do not use the sensor if subjected to a drop or other mechanical shock.
  3. 3) Electro static discharge
    ESD (Electro Static Discharge) may affect sensor characteristics. Exercise precaution against ESD during handling of sensors. Take appropriate measures against ESD especially in handling MEMS type sensors.
  4. 4) No soaking
    Avoid contact with water. Sensor characteristics may be affected due to soaking or splashing the sensor with water.
  5. 5) No disassembly or deformation
    Under no circumstances should the sensor be disassembled, nor should the sensor structure be deformed. Such action would void the sensor warranty.
  6. 6) Gas inlet
    Do not block the gas inlet of sensor. The sensor would not work properly with a clogged inlet.

【 Mounting process 】

  1. 1) Soldering
    Manual soldering is recommended. High concentrations of flux or excessive soldering heat may affect sensor characteristics. When wave soldering is used, rosin flux with minimal chlorine should be used, and a trial assembly test should be conducted before production starts to see if there would be any influence to sensor characteristics.
  2. 2) Resin coating
    When a resin coating is applied on a printed circuit board for improving its resistance to moisture, the chemical solvent contained in the coating material may affect sensor characteristics. Sample testing should be conducted to see if this process would adversely affect sensor characteristics.
  3. 3) Electro static discharge
    Exercise necessary precaution against ESD during mounting of the sensors on finished instruments.
  4. 4) Resonance
    Excessive vibration may cause damage of the sensor structure or breakage of the sensor components at the resonance frequency. Usage of compressed air drivers or ultrasonic welders on assembly lines may cause such vibration to the sensor. Before using such equipment, preliminary tests should be conducted to verify that there will be no influence on sensor characteristics.

【 Application design 】

  1. 1) Storage for a ling time
    When a sensor or a finished instrument incorporating the sensor is stored without powering for a long period, sensor characteristics may be affected according to the storage environment.
  2. 2) Preheating time
    As unpowered storage becomes longer, a longer preheating period is required to stabilize the sensor before usage.
  3. 3) Heat generation
    The gas sensor generates heat. A temperature sensor or a humidity sensor mounted close to the gas sensor may result in erroneous temperature or humidity measurement. Temperature and humidity sensors should be mounted at a sufficient distance from the gas sensor.
  4. 4) Explosion protection
    The sensor does not fulfill technical requirements of industry standards for explosion protection. When the sensor will be used in explosive atmospheres, consider using an appropriate external explosion-proof enclosure according to the zone classification of where the sensor is intended to be used.
  5. 5) Foreign conductive objects
    If foreign conductive objects get into the sensor, short-circuit may occur inside the sensor. When such conditions are expected to be encountered, installation of an external air filter is recommended.
  6. 6) Fitness for purpose
    Before usage of the sensor, customers should verify and ensure that the sensor will work properly under the conditions where they intend to use it and that the sensor is fit for the purpose for which customers wish to use it.