Sniffing/puffing can get you high and is addicting. I'm unsure if you can get that using dettol, but I wouldn't be surprised given how strong some of those cleaners are. I suggest you pop over to the addicts community.
http://www.medhelp.org/forums/Addiction-Substance-Abuse/show/77 They might be able to give you some good info.
Also sniffing can be disastrous for your health so when you're ready to come clean talk to your dr. You may have some damage in your nasal passages. If you get a very very bad headache or start bleeding excessively from the nose you should get to the ER. Be sure to admit to the dr's about this since it might help with the treatment. Also remember there is nothing the dr's haven't seen so no need to be ashamed.