Method and system for a filter

A method of determining particle transmittance of a filter in a particle detection system, the method comprising the steps of:

• detecting a level of first particles having a size indicative of smoke particles and which particles are suspended in air passing through the detection system;
• determining the flow rate of air passing through the detection system;
• determining an integrated smoke hours value by integrating the detected level of first particles over time;
• determining an estimated smoke particle transmittance of the filter in accordance with an operation comprising multiplying the integrated smoke hours value with the determined flow rate.

A method of determining particle transmittance of a filter in a particle detection system, the method comprising the steps of

• detecting a level of first particles having a size indicative of smoke particles and which particles are suspended in air passing through the detection system;
• determining the flow rate of air passing through the detection system;
• determining a smoke hours value corresponding to the detected level of first particles;
• determining an estimated smoke particle transmittance of the filter in accordance with an operation comprising multiplying the smoke hours value with the determined flow rate and integrating the operation over time.

A method of indicating particle transmittance including:

• detecting the amount of smoke passing through a detection chamber
• summing the amount of detected smoke passing through the detection chamber over time to ascertain total integrated smoke hours;
• comparing the total amount of smoke passed through the detection chamber with a predetermined value;
• sending a signal indicating when the total integrated smoke hours has exceeded the predetermined value.