Method and system for controlling air quality in an indoor environment of a building

1. A method of controlling air quality in an indoor environment of a building by a system that comprises a carbon dioxide sensor configured to detect an instantaneous value of carbon dioxide concentration in the air of the indoor environment of the building, a control unit in signal communication with the carbon dioxide sensor, a communication unit for establishing signal communication between the carbon dioxide sensor and the control unit, and a storage unit in signal communication with the control unit, the method comprising the steps of:

a) defining and storing in the storage unit, by the control unit, control values of carbon dioxide concentration;

b) detecting, by the carbon dioxide sensor, an instantaneous value of carbon dioxide concentration and sending, by the communication unit, said instantaneous carbon dioxide concentration value to the control unit;

c) processing, by the control unit, the control values and the instantaneous values of carbon dioxide concentration to generate an output signal representative of the processing performed by the control unit;

d) sending, by the control unit the output signal to a visual and/or acoustic warning unit;

said method being characterized in that:

the step a) comprises the steps of:

a1) defining and storing in the storage unit an activation value of carbon dioxide concentration;

a2) defining and storing in the storage unit a critical value of carbon dioxide concentration, said critical value of carbon dioxide concentration being greater than said activation value of carbon dioxide;

a3) defining and storing in the storage unit an acceptable value of carbon dioxide concentration, said acceptable value of concentration being smaller than the critical value of carbon dioxide concentration and greater than the activation value of carbon dioxide concentration;

the step c) comprises the step c1) of comparing the instantaneous value of carbon dioxide concentration with the activation value of carbon dioxide concentration, with the critical value of carbon dioxide concentration and with the acceptable value of carbon dioxide concentration; wherein

the output signal is representative of a first alert in which the instantaneous value of carbon dioxide concentration is lower than the activation value of carbon dioxide concentration;

the output signal is representative of a second alert in which the instantaneous value of carbon dioxide concentration is higher than the activation value of carbon dioxide concentration and is lower than the critical value of carbon dioxide concentration;

the output signal is representative of a third alert in which the instantaneous value of carbon dioxide concentration is higher than the critical value of carbon dioxide concentration and said instantaneous value of carbon dioxide concentration remains constant or increases with time;

the output signal is representative of a fourth alert once the instantaneous value of carbon dioxide concentration has exceeded the critical value of carbon dioxide concentration and in which the instantaneous value of carbon dioxide concentration decreases with time and is higher than the acceptable value of carbon dioxide concentration.

2. A method as claimed in claim 1 wherein the system further comprises a temperature sensor configured to detect an instantaneous value of air temperature in the indoor environment, said temperature sensor being in signal communication with the control unit via the communication unit,

said method comprising, after the step b) and before the step c), the steps of:

detecting, by the temperature sensor, an instantaneous value of air temperature in the indoor environment and sending, by the communication unit said instantaneous value of temperature to the control unit;

defining, by the control unit, a refresh time interval comprising a plurality of time points;

storing in the storage unit, by the control unit, an instantaneous value of temperature for each time point of the refresh time interval to define a set of instantaneous values of temperature;

storing in the storage unit, by the control unit, an instantaneous value of carbon dioxide concentration for each time point of the refresh time interval to define a set of instantaneous values of carbon dioxide concentration.

3. A method of controlling air quality in an indoor environment of a building by a system that comprises a carbon dioxide sensor configured to detect an instantaneous value of carbon dioxide concentration in the air of the indoor environment of the building, a control unit in signal communication with the carbon dioxide sensor, a communication unit for establishing signal communication between the carbon dioxide sensor and the control unit, and a storage unit in signal communication with the control unit, the method comprising the steps of:

a) defining and storing in the storage unit, by the control unit, control values of carbon dioxide concentration;

b) detecting, by the carbon dioxide sensor, an instantaneous value of carbon dioxide concentration and sending, by the communication unit, said instantaneous carbon dioxide concentration value to the control unit;

c) processing, by the control unit, the control values and the instantaneous values of carbon dioxide concentration to generate an output signal representative of the processing performed by the control unit;

d) sending, by the control unit the output signal to a visual and/or acoustic warning unit;

said method being characterized in that:

the step a) comprises the steps of:

a1) defining and storing in the storage unit an activation value of carbon dioxide concentration;

a2) defining and storing in the storage unit a critical value of carbon dioxide concentration, said critical value of carbon dioxide concentration being greater than said activation value of carbon dioxide;

a3) defining and storing in the storage unit an acceptable value of carbon dioxide concentration, said acceptable value of concentration being smaller than the critical value of carbon dioxide concentration and greater than the activation value of carbon dioxide concentration;

the step c) comprises the step c1) of comparing the instantaneous value of carbon dioxide concentration with the activation value of carbon dioxide concentration, with the critical value of carbon dioxide concentration and with the acceptable value of carbon dioxide concentration; wherein

the output signal is representative of a first alert as long as the instantaneous value of carbon dioxide concentration is lower than the activation value of carbon dioxide concentration;

the output signal is representative of a second alert as long as the instantaneous value of carbon dioxide concentration is higher than the activation value of carbon dioxide concentration and is lower than the critical value of carbon dioxide concentration;

the output signal is representative of a third alert as long as the instantaneous value of carbon dioxide concentration is higher than the critical value of carbon dioxide concentration and said instantaneous value of carbon dioxide concentration remains constant or increases with time;

the output signal is representative of a fourth alert once the instantaneous value of carbon dioxide concentration has exceeded the critical value of carbon dioxide concentration and as long as the instantaneous value of carbon dioxide concentration decreases with time and is higher than the acceptable value of carbon dioxide concentration;

wherein the system further comprises a temperature sensor configured to detect an instantaneous value of air temperature in the indoor environment, said temperature sensor being in signal communication with the control unit via the communication unit,

said method comprising, after the step b) and before the step c), the steps of:

detecting, by the temperature sensor, an instantaneous value of air temperature in the indoor environment and sending, by the communication unit said instantaneous value of temperature to the control unit;

defining, by the control unit, a refresh time interval comprising a plurality of time points;

storing in the storage unit, by the control unit, an instantaneous value of temperature for each time point of the refresh time interval to define a set of instantaneous values of temperature;

storing in the storage unit, by the control unit, an instantaneous value of carbon dioxide concentration for each time point of the refresh time interval to define a set of instantaneous values of carbon dioxide concentration;

after the step b) and before the step c), the steps of:

defining, by the control unit, a reference value of temperature;

analyzing, by the control unit, the set of instantaneous values of temperature to determine a maximum value of temperature from said instantaneous values of temperature;

analyzing, by the control unit, the set of instantaneous values of temperature to determine a rate of decrease of temperature;

defining, by the control unit, a maximum air purification time interval according to the maximum value of temperature, the reference value of temperature and the rate of decrease of temperature;

the step c) comprises the steps of:

c2) defining, by the control unit, a critical time interval corresponding to the period of time in which the output signal is representative of the fourth alert;

c3) comparing, by the control unit, the critical time interval with the maximum air purification time interval;

c4) setting the output signal to the second alert if the critical time interval exceeds the maximum air purification time interval.

4. A method as claimed in claim 3 comprising, after the step b) and before the step c), the steps of:

defining, by the control unit, a reference time interval and a comfort value of carbon dioxide concentration in the air of the indoor environment of the building;

analyzing, by the control unit, the set of instantaneous values of carbon dioxide concentration to determine a rate of increase of carbon dioxide concentration;

calculating, by the control unit, an actual time interval according to the critical value of carbon dioxide concentration, the acceptable value of carbon dioxide concentration and the rate of increase of carbon dioxide concentration;

comparing, by the control unit, the actual time interval with the reference time interval;

refreshing, by the control unit, the acceptable value of carbon dioxide concentration according to the comfort value of carbon dioxide concentration, the reference time interval, the actual time interval and the rate of increase of carbon dioxide concentration if the actual time interval is shorter than the reference time interval.

5. A method as claimed in claim 4 , comprising, after the step of refreshing the acceptable value of carbon dioxide concentration and before the step c):

defining, by the control unit, a value of carbon dioxide concentration outside the building;

comparing, by the control unit, the acceptable value of carbon dioxide concentration with the outside value of carbon dioxide concentration;

refreshing, by the control unit, the acceptable value of carbon dioxide concentration according to the outside value of carbon dioxide concentration and refreshing, by the control unit, the critical value of carbon dioxide concentration according to the critical value of carbon dioxide concentration stored in the storage unit, the reference time interval, the outside value of carbon dioxide concentration and the rate of increase of carbon dioxide concentration, if the acceptable value of carbon dioxide concentration exceeds the outside value of carbon dioxide concentration by a value that is equal to a specific value of carbon dioxide concentration, preferably equal to 200 ppm.

6. A method as claimed in claim 5 , comprising, after the step of refreshing the acceptable and critical values of carbon dioxide concentration and before the step c), the additional steps of:

defining, by the control unit, an air purification time interval according to the critical value of carbon dioxide concentration, the acceptable value of carbon dioxide concentration and the rate of decrease of carbon dioxide concentration;

defining, by the control unit, a minimum attainable value of temperature according to the maximum value of temperature, the purification time interval and the rate of decrease of temperature;

comparing, by the control unit, the minimum attainable value of temperature with the reference value of temperature;

refreshing, by the control unit, the acceptable value of carbon dioxide concentration according to the critical value of carbon dioxide concentration, the air purification time interval and the rate of decrease of carbon dioxide concentration, if the minimum attainable value of temperature is smaller than the reference value of temperature.

7. A method as claimed in claim 1 , wherein the step d) comprises the step d1) of sending the output signal from the control unit to a light source, the first, second, third and fourth alerts corresponding to a first, a second, a third and a fourth light colors and/or intensities that can be emitted from the light source respectively.

8. A method as claimed in claim 1 , wherein the step d) comprises the step d2) of sending the output signal from the control unit to a sound source, the first, second, third and fourth alerts corresponding to a first, a second, a third and a fourth sound tones and/or intensities respectively.