They can asphyxiate in confined spaces, and they are not suitable for deep fat fryers, as the strong jet from the extinguisher can carry the burning fat out of the fryer. Fires can quickly re-ignite ...

It shouldn't harm your experiment. You now have a CO2 fire extinguisher! Return to your candles (you might need to drying off first), fire extinguisher in hand, and now you can light your candles.