Freon is indeed toxic at sufficient concentration but unless you try to get high with it I doubt shooting with red gaz will do any real damage
For me if it's available : CO², less leaks due to cartridge design and power is more stable... and and KJW GBB you can still use it when temperature is down to -18°C (my famous freezer test

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Tous les jours nous nous endormons plus instruits mais pas forcément moins bêtes...
I can do a CTRL+ATL+DEL on your gun !
Gun doc in Montreal on AEG, GBB, GBBR and Bolt rifle (gaz and spring)
Heavy custom builder (including painting)