Modular filter assembly

1. An air treatment assembly for treating air passing through an air duct, the air treatment assembly adapted for installation in the air duct and comprising:

a frame defining an interior space and an inlet opening providing access to the interior space, and having one of a keyway and a key; and

an air treatment medium adapted to be inserted into the interior space through the inlet opening, and having the other of the keyway and the key;

wherein the key comprises an extension of one of the frame and the air treatment medium, the key having a selected configuration, and the keyway comprising a seat having a configuration complementary to the configuration of the key for coupling of the key with the keyway, the key coupled with the keyway defining a keyed connection;

wherein the keyed connection enables the air treatment medium to be constrained in the frame solely in a single preselected orientation.

2. The air treatment assembly according to claim 1 , wherein the keyed connection is provided between the inlet opening and the air treatment medium to control the insert orientation of the air treatment medium into the insert opening.

3. The air treatment assembly according to claim 2 , wherein each of the air treatment medium and the inlet opening have an irregular cross-section to form the key and keyway.

4. The air treatment assembly according to claim 3 , wherein the irregular cross-sections are complementary.

5. The air treatment assembly according to claim 1 , wherein the frame is sized to be slidably inserted into a standardized opening in the air duct.

6. The air treatment assembly according to claim 5 , wherein the air treatment medium has opposing faces and the keyed connection controls the orientation of the opposing faces relative to the direction of air flow in the duct.

7. The air treatment assembly according to claim 1 , wherein the air treatment medium comprises at least one of: an air filter, an ionizer, and an electrostatic precipitator.

8. The air treatment assembly according to claim 1 , and further comprising an air quality module removably mounted to the frame.

9. The air treatment assembly according to claim 8 , wherein the air quality module is removably mounted to the frame independent of the air treatment medium.

10. The air treatment assembly according to claim 1 , wherein the keyed connection is provided between the inlet opening and the air treatment medium to control the size of the air treatment medium relative to the inlet opening.

11. The air treatment assembly according to claim 1 , wherein the extension comprises one of a flange, a beveled surface, and a post.

12. The air treatment assembly according to claim 1 , wherein the seat comprises one of a rabbet, a beveled surface, and an aperture.

13. An air treatment assembly for treating air passing through an air duct, the air treatment assembly comprising:

a frame defining an interior space divided into a first section and a second section;

an air treatment medium for treating air, and associated with the first section; and

an air quality module for providing air treatment supplemental to that provided by the air treatment medium, adapted to be removably coupled with the second section independently of the state of the air treatment medium relative to the first section.

14. The air treatment assembly according to claim 13 , wherein the air quality module comprises an air scent release module.

15. The air treatment assembly according to claim 13 , wherein the air quality module comprises a temperature sensing module.

16. The air treatment assembly according to claim 13 , wherein the air quality module comprises a humidity sensing module.

17. The air treatment assembly according to claim 13 , wherein the air quality module comprises an air pressure transducer.

18. The air treatment assembly according to claim 13 , wherein the air quality module comprises a power distribution module.

19. The air treatment assembly according to claim 13 , wherein the frame has an inlet opening providing access to at least the first section of the interior space and the air treatment medium is sized to be inserted through the inlet opening.

20. The air treatment assembly according to claim 13 , and further comprising a keyed connection between the frame and the air treatment medium to constrain the air treatment medium in the frame solely in one direction relative to the direction of air passage.

21. The air treatment assembly according to claim 13 , wherein the frame is sized to be slidably inserted into a standardized opening in the air duct.

22. An air treatment assembly for treating air flowing through an air duct, the air treatment assembly comprising:

a frame defining an interior space, having a first frame member and an insert opening through the first frame member to provide access to the interior space, the frame being insertable into the air duct solely in a preselected orientation;

an air treatment medium having an upstream face toward which air flows and a downstream face away from which air flows, and adapted to be received within the interior space through the insert opening solely in a preselected orientation; and

a keyed connection comprising a key and a keyway configured so that coupling of the air treatment medium with the frame constrains the air treatment medium in the frame when the frame is inserted into the air duct so that the upstream face is oriented in an upstream direction relative to the direction of air flow.