Used Magnesium Carbonate in Pirex boiling tube in FUME cupboard

The thermal decomposition of nitrate magnesium

2Mg(NO3)2  2MgO + 4NO2 + O2

The thermal decomposition of nitrate magnesium to produce magnesium oxide, nitrogen dioxide and oxygen. This reaction takes place at a temperature of over 300°C.

Source: https://chemiday.com/en/reaction/3-1-0-1720