For fire safety there should be no heating cooling returns in what part of house?

Attics.

Attics are often used as storage space, but they can also be a fire hazard. This is because attics are typically not well-ventilated, and they can accumulate heat and smoke. If a fire starts in an attic, it can quickly spread to the rest of the house.

For this reason, it is important to avoid installing heating or cooling returns in attics. These returns can allow hot air and smoke to circulate throughout the house, which can increase the risk of a fire.

Instead, heating and cooling returns should be installed in other parts of the house, such as bedrooms, living rooms, and kitchens. These rooms are typically better ventilated, and they are less likely to accumulate heat and smoke.