Are Halon fire protection systems still in use?

Halon fire protection systems were widely used due to their effectiveness in extinguishing fires without leaving residue, which made them particularly appealing for use in sensitive environments like data centers and aircraft. However, the production and use of Halon have been significantly restricted due to its detrimental effects on the ozone layer, following international agreements such as the Montreal Protocol. As a result, although Halon systems that were already in place may still be operational, the construction of new Halon systems is prohibited. This explains why the correct choice indicates that, while existing systems continue to operate in some contexts, there are no new systems being constructed due to concerns over ozone damage.