Dogs and cats are a part of millions of U.S. families today, an indispensable element in our homes and lives.

But do we think of them as part of the family when we decide to turn the thermostat up or down, or take note of what they “contribute” to our ventilation systems?

Most pet animals shed, and with all that hair comes dander (shed skin particles), which is light and easily carried by air currents in the house. (Birds also have dander and the feathers they shed are just as portable as hair.) Most of this animal matter—to which many people are allergic—ends up in the furnace filter and can affect the efficiency of air and heat circulation. Pet-owners need to change air filters more frequently than non-pet-owners; those with many pets need to do so more frequently than those with just one.

Dogs and cats don’t have sweat glands on their bodies like humans. This means that although they can tolerate somewhat higher or lower temperatures than we may like (60–65° F. as a low range and 78–80° F. as a high), they can’t regulate body heat as humans can, and mere air circulation, as with fans, doesn’t help them and may even dehydrate them. Pet-owners need to remember that what’s fine for them may be nearly intolerable for Fido or Puss and adjust temperatures accordingly. Pets should not be left in a house with no heat in winter and no cooling in summer, although the necessary temperature settings may be somewhat higher or lower than we prefer.

Finally, pet-owners—mainly dog-owners—need to keep animals away from outdoor HVAC condensers, which are usually conveniently located in backyards near the kitchen door, the typical entry/exit route for pets. Buildup of animal urine on condenser exteriors can cause deterioration and require replacement regularly.