Capacitance and flammable liquid I'm trying to attach a sensor to some tubes to measure the level of liquids in them. 

see here

One tube contains toluene and the other contains Recosol R55 (shellite). 

I'm thinking of using a capacitance level sensor like this or this.

But I am concerned about the safety of doing this. Could the capacitance sensor ignite these liquids? is this even possible? 

Obviously I need to check with the suppliers of the device. However, most of datasheets for level sensors omit this information. Perhaps they are not game enough to make any claims about their sensor in this regard. 

I don't really understand capacitance and whether it can ignite flammable liquids.
The capacitance sensor itself will certainly not present an ignition risk to your system. The sensor will be on the outside of the container, and it does not introduce any electrical potential that would cause a spark. 

The way the device works is to measure the change in the sensor's capacitance depending on the dielectric effect of the liquid, which will increase as more liquid enters the electric field of the sensor (a capacitor).