Ventilation system with humidity responsive ventilation controller

1. A method of controlling ventilation comprising:

determining a current gradient including:

receiving a first humidity level from a humidity sensor in communication with a ventilation controller;

waiting a first time delay;

receiving a second humidity level from the humidity sensor; and

calculating a first gradient based on a first humidity difference, wherein the first humidity difference is a difference between the second humidity level and the first humidity level, wherein the current gradient is based on the first gradient;

comparing the current gradient to a threshold gradient; and

activating a device coupled to a ventilation controller if the current gradient is greater than or equal to the threshold gradient.

2. The method of claim 1 , wherein the ventilation controller includes a housing including:

a circuit for electrically connecting a power source to the ventilation controller;

at least one switch in the housing; and

at least one humidity sensor in communication with, and providing data to, the ventilation controller.

3. The method of claim 1 , wherein the ventilation controller includes at least one of a display, an electrical receptacle, a speaker, a motion detector, a light or a fragrance dispenser.

4. The method of claim 1 , wherein the device includes at least one of a fan or a light.

5. The method of claim 1 , wherein the current gradient is equal to the first gradient.

6. The method of claim 1 , wherein determining the current gradient further includes:

waiting a second time delay from receiving the second humidity level;

receiving a third humidity level; and

calculating a second gradient based on a second humidity difference wherein the second humidity difference is a difference between the third humidity level and the second humidity level, wherein comparing the first gradient to the first threshold gradient further includes comparing the second gradient to a second threshold gradient if the first gradient is greater than or equal to the first threshold gradient.

7. The method of claim 1 , wherein determining a current gradient further includes:

receiving a third humidity level;

waiting a second time delay;

receiving a fourth humidity level; and

calculating a second gradient based on a second humidity difference, wherein the second humidity difference is a difference between the fourth humidity level and the third humidity level, wherein comparing the first gradient to the first threshold gradient further includes comparing the second gradient to a second threshold gradient if the first gradient is greater than or equal to the first threshold gradient.

8. The method of claim 1 , wherein the threshold gradient includes a pre-selected threshold gradient.

9. The method of claim 1 , wherein the threshold gradient includes retrieving a plurality of recorded humidity levels over a time interval.

10. The method of claim 9 , wherein the time interval includes a plurality of time intervals and wherein the plurality of recorded humidity levels includes retrieving a plurality of recorded humidity levels in each of the plurality of time intervals and wherein determining an average humidity level includes constructing a humidity profile.

11. The method of claim 1 , wherein comparing the current gradient to the threshold gradient includes determining an average humidity level gradient, wherein the threshold gradient is based on the average humidity level gradient.

12. The method of claim 1 , wherein comparing the current gradient to the threshold gradient includes determining the threshold gradient from at least one of a linear curve, non-linear curve, piecewise linear curve, piecewise non-linear curve, or a combination of a linear curve and non-linear curve.

13. The method of claim 1 , further comprising deactivating the device.

14. The method of claim 13 , wherein deactivating the device includes:

waiting a first shutdown time delay; and

interrupting power to the device.

15. A method of controlling ventilation comprising:

receiving a first humidity level;

waiting a first time delay;

receiving a second humidity level;

calculating a first gradient based on a first humidity difference divided by the first time delay, wherein the first humidity difference is a difference between the second humidity level and the first humidity level;

receiving a third humidity level;

waiting a second time delay;

receiving a fourth humidity level;

calculating a second gradient based on a second humidity difference divided by the second time delay, wherein the second humidity difference is a difference between the fourth humidity level and the third humidity level;

comparing the first gradient to a first threshold gradient;

comparing the second gradient to a second threshold gradient if the first gradient is greater than or equal to the first threshold gradient; and

activating a device coupled to the ventilation controller if the second gradient is greater than or equal to the second threshold gradient.

16. A ventilation system comprising:

an exhaust fan; and

a ventilation controller contained within a housing, the housing including:

a first humidity sensor being exposed to at least one external surface of the housing;

the ventilation controller coupled to the exhaust fan and including:

logic for determining a current gradient including:

logic for receiving a first humidity level from a humidity sensor in communication with a ventilation controller;

logic for waiting a first time delay;

logic for receiving a second humidity level from the humidity sensor; and

logic for calculating a first gradient based on a first humidity difference, wherein the first humidity difference is a difference between the second humidity level and the first humidity level, wherein the current gradient is based on the first gradient;

logic for comparing the current gradient to a threshold gradient; and

logic for activating the exhaust fan if the current gradient is greater than or equal to the threshold gradient.

17. The system of claim 16 , further comprising at least one switch, the at least one switch including a manual switch, the manual switch operable to bypass the ventilation controller.

18. The system of claim 16 , wherein-the current gradient is equal to the first gradient.

19. The system of claim 16 , wherein the logic for determining the current gradient further includes:

logic for waiting a second time delay from receiving the second humidity level;

logic for receiving a third humidity level; and

logic for calculating a second gradient based on a second humidity difference, wherein the second humidity difference is a difference between the third humidity level and the second humidity level.

20. The system of claim 19 , wherein the logic for comparing the first gradient to the first threshold gradient further includes logic for comparing the second gradient to a second threshold gradient if the first gradient is greater than or equal to the first threshold gradient.

21. The system of claim 16 , wherein the logic for determining a current gradient further includes:

logic for receiving a third humidity level;

logic for waiting a second time delay;

logic for receiving a fourth humidity level; and

logic for calculating a second gradient based on a second humidity difference, wherein the second humidity difference is a difference between the fourth humidity level and the third humidity level.

22. The system of claim 21 , wherein the logic for comparing the first gradient to the first threshold gradient includes logic for comparing the second gradient to a second threshold gradient if the first gradient is greater than or equal to the first threshold gradient.