Are you writing about the "SMART MT500" gas sensing device?

See page 17 of the manual ( http://ses-enser.com/users/files/products_asa/SES_ENSER--Operating_Manual_MT500.pdf ) - there the "poisons" affecting the catalytic and presumably the electrochemical detectors. The IR detector may be susceptible to contamination by dust.

The components that can damage a sensing device depend on the individual devices properties and vary usually from device to device. Thus you have to understand how an individual device operates to find the critical substances etc.

Most of these 'attacks' cannot be fixed other than by replacing the sensing element from time to time: you may think about filters, but usually these filters also affect the components that you want to detect. (Imagine sealing the sensor hermetically: it would be protected perfectly - on the other hand being completely useless as the components to be detected would not reach the sensor as well.)

Hope this helps

thanks , 

The sensor is about 3 years in the cellar has been kept in a box. Now that I opened it I see that does not work !!

Ok - so it is about the electronics, not about the sensing device.

Quite difficult to assess from the distance ...

Had the sensor been used before? (probably already 'dead' when stored)

What about the humidity level in the cellar?

I didn't check in detail: are there fuses that might be blown?

Regards

As soon as the purchase and transfer of sensor,  that is stored in the cellar about 3 years. The sensor in it's package, with several other electronic and mechanical equipment in a large wooden packages have been kept. There are no any control on temperature, humidity and .. . On other hand, the temperature up to 60 degrees, high humidity and dirt on most days.

Was the sensor packaged "hermetically sealed" - eventually with some desiccant bag? 60 °C shouldn't damage the device and dirt should not be an issue if packaged in some plastics. Humidity could be an issue if not hermetically sealed.

Another topic: is the device "completely dead" ?

I looked into the manual and found that it should suffice to connect the supply (24 V DC, connector position #4) and ground ("0 V", pos. #11). While the sensor might be reverse polarity protected, it will not work if polarity is reversed. Depending on the state of your wire connection, it might help to check the supply directly at the connector with a multimeter.