Apparatus and associated methods for detecting air-borne particles

An apparatus comprising:

• a body having an aperture dimensioned to receive a first air-borne particle of a size corresponding to the aperture therethrough and further dimensioned to not receive a second air-borne particle of a size greater than the size corresponding to the aperture therethrough;
• first and second electrodes not in contact with each other and positioned on or within one or more walls defining the aperture between which a potential difference can be applied, wherein each of the first and second electrodes does not extend across the aperture, and wherein each of the first and second electrodes is not extended off a surface defining the one or more walls;
• and
• a measurement circuit configured to measure an electrical property between the first and second electrodes such that the presence of the first air-borne particle within the aperture can be detected based on a change in the electrical property when the first air-borne particle contacts both the first and second electrodes and such that the second air-borne particle is prevented from contacting both the first and second electrodes.