There are fireplaces located throughout Hogwarts; they are in the Great Hall, the common rooms, the Professors’ offices, the Divination classroom etc. The fireplaces at Hogwarts are not usually connected, but they can be (Pm). For example, Snape is able to use his fireplace to contact Lupin (PA14).
The fireplaces appear to be the main source of heat for the castle: “While the Gryffindor common room and the Great Hall had roaring fires, the draughty corridors had become icy and a bitter wind rattled the windows in the classrooms” (PS12).
- Professor McGonagall's office has a fireplace with a mantelpiece (CS8). This fireplace can be connected to the Floo Network when necessary (HBP18).
- While in hiding, Sirius Black talked to Harry by means of a wizard fireplace (GF19).
- Snape used a powder thrown into the fire in his office fireplace to contact Lupin and ask to speak to him (PA14).
- When the Ministry wanted to spy on all communication in and out of Hogwarts, they employed the Floo Regulation Board to monitor the Hogwarts fires (OP27, OP28).
- Harry took a risk and spoke to Sirius, Lupin and Kreacher through the fireplaces at Hogwarts anyway (OP28, OP29, OP32).
- During Harry's first Divination class, the Divination classroom was “stiflingly warm” due to the fireplace being lit to heat “a large copper kettle”, which gives off a “sickly” perfume (PA6).