Jilin Baoyuanfeng Poultry Industry Co., Ltd. had a serious fire on June 3rd. One of the main reasons is that there is no flame retardant magnesium hydroxide added to combustible building materials.

A, the decomposition products of Mg(OH) 2 can isolate combustible materials from oxygen or air, so A is correct;

B, Mg(OH) 2 decomposes and absorbs heat, which can reduce the temperature below the ignition point of combustible materials, so B is correct;

C, the ignition point is the inherent property of the material, generally will not change, can only change the temperature of combustible materials, so the statement of C is wrong;

D, MgCO 3 is easier to decompose than Mg(OH) 2, and magnesium oxide and carbon dioxide can also be used as flame retardants, so D is correct;

So choose C.