I had a halon extinguisher & got the guilts about using it & the damage to the environment so I took it to a hospital where I work so it could be sent for 'proper' disposal (they have a large fire extinguisher maint program).

The maintenance engineer laughed at me & said 'proper disposal' consisted of authorised people venting all the gas to the atmosphere as opposed to unauthorised people.

If it meets the regs just use it, hopefully you never have to! Halon & Co 2 work in exactly the same way, they both displace oxygen. - John.