Using a collection material for fumes can be quite effective, but it requires additional data.
Sampling rate is one.
Most such monitors flow from 0.5 liters per minute to 5 LPM whereas human breathing rate at a light workload is 40 LPM and at complete rest about 25 LPM. Easy to compensate for that.
Using a collection media presents an accumulative measurement, so for example if a flight is 8 hours in duration it is important to know the duration of exposure (i.e. 30 minutes) or the sample will be diluted by the ratio between the two.
If the collection media is not replaced frequently (between each flight) trace and non-concerning concentrations will be added to sample over time and consequently distort the results.
Install a photoionization detector (PID) with a 9.6eV lamp and a datalogger.
It is cheap (~$2,000) and will pick up countless compounds, though not specifically.
A PID is excellent in detecting long chained HC's like oil, it is real time and can log 100's of hours by the minute.
Down side it should be calibrated at least monthly; a 2 minute and 99% automatic procedure.