Propane Sensors

TF9-60This sensor is about the size of a dime (0.65" D) and used in our GS/5 & GS/6 detectors.


small sensorThis sensor is about the size of a pencil eraser (0.32" D) and is used in our GS/3 propane detectors.


These sensors can be contaminated by water.

If the sensor gets wet, the water causes a short circuit in the sensor. The result is the same as propane completing the sensor circuit and triggers an alarm.

It is extremely important to keep the sensor dry at all times.

Not-Too-Technically Speaking: How it Works

At the heart of every propane detector is the sensor and all of them function in the same basic way.

The sensor uses the difference between the electrical properties of oxygen and propane to trigger an alarm.

The miniature sensor contains 2 main components. One is a layer of metal oxide semiconductor material - usually tin dioxide. The second is a miniature heater which keeps the semiconductor at a constant high temperature - around 400°C - which it needs to function properly.

The metal oxide's ability to conduct an electrical current (its resistance) is effected by gasses which are attracted to its surface. In a propane detector's sensor the 2 gasses involved are oxygen and propane.

Oxygen has the ability to trap electrons, which increases the resistance of the metal oxide. Propane, on the other hand, improves the flow of an electric current through the metal oxide and lowers its resistance.

Depending on the concentration or absence of propane in the air around the sensor the current through the metal oxide will increase or decrease - the higher the level of propane the greater the current. When propane reaches a dangerous level - 25% of the lower explosive level, or LEL - the detector begins to sound an alarm. In other words, the alarm starts while you still have a 75% margin of safety. This safety margin decreases as the propane concentration rises.

The alarm circuit can be as simple as an audible alarm and flashing red LED (GS/3) or as elaborate as propane shut-off (GS/6).