Abstract: A method of estimating occupancy of a room, comprising: acquiring a plurality of measurements of an aspect of air quality in the room; and estimating the occupancy of the room based on the plurality of measurements and a room ventilation rate parameter. By estimating the occupancy of the room based on aspects of air quality, it is possible to detect occupancy based on data from sensors which may already be present for other purposes (e.g. for measuring air quality). Combining measurements of air quality with knowledge related to ventilation rate results in information indicative of the occupancy. Estimating the number of people in the room allows detailed analysis and control to be undertaken. Such occupancy data can also be used to control other services, e.g. to control the ventilation or to provide information about the number of people present.

Abstract: A radon gas sensor comprising: a diffusion chamber; a photodiode positioned inside the diffusion chamber; and a photomultiplier positioned inside the diffusion chamber; wherein a scintillating material is provided on at least a part of an inner surface of the diffusion chamber. The photomultiplier detects more alpha particles, but cannot distinguish the energies of different alpha particles. On the other hand, the photodiode can distinguish different decays because the magnitude of the signal generated by the photodiode is proportional to the kinetic energy of the alpha particle striking it. Thus, the photodiode produces spectral data. The spectral data is used to estimate the amount of Polonium that is adhering to aerosols. This is used to apply a correction factor to the data to provide a better estimate of the true Radon concentration in the chamber. This can be combined with the count data of the photomultiplier for overall improved data.

Abstract: A sensor comprising: a printed circuit board; a photosensor mounted on a first side of the printed circuit board; and a light source mounted on a second, opposite side; wherein the light source is arranged to transmit light through at least a portion of the printed circuit board, which is impermeable to air. Positioning of the light source on the opposite side of the printed circuit board from the photosensor means that the bulk of the printed circuit board lies between the light source and the photosensor, obstructing direct transmission of light from the light source to the photosensor. However, light can be transmitted through the printed circuit board itself without drilling a hole through the printed circuit board. In this way, the light source can be mounted on the opposite side of the printed circuit board from the photosensor while still transmitting light to the photosensor.

Abstract: A sensor, comprising: a printed circuit board; a detector mounted on the printed circuit board; an inner dome that is electrically conductive and is mounted on the printed circuit board so as to form a diffusion chamber around the detector; and an outer dome that is electrically conductive and surrounding the inner dome. The dual dome construction allows a stronger electric field to be generated inside the inner dome. The strength of the electric field is determined by the voltage of the detector, the voltage of the inner dome and the distance between them. The detector has a maximum voltage that can safely be applied to it without damaging the detector. With the dual dome design, the inner dome can be biased to a higher potential, thereby increasing the strength of the electric field inside the inner dome, while still shielding that high voltage via the outer dome.

Abstract: A method of measuring a radon concentration or a radon exposure level comprising: placing a plurality of individual radon measurement instruments at locations, each instrument being capable of data output; receiving radon measurement data from each of said plurality of instruments; combining said data from said plurality of instruments into a single data set; and calculating a radon concentration or radon exposure value from said single data set. Using a plurality of individual detectors and combining their data provides a much better overall analysis of radon concentration or radon exposure level. The calculated value may include producing an average of the radon concentrations across the multiple instruments. The average may be weighted with weights determined according to different locations such as proximity to ventilation devices or based on the time that an average user spends in each location.

Abstract: A gas sensor instrument comprises a housing formed of two parts (102, 10) and a diffusion chamber inside the housing. The diffusion chamber is formed from two parts (106, 108) and at least one of the diffusion chamber parts is formed integrally with one of the housing parts. This allows a reduction in size of the instrument without compromising the size of the diffusion chamber. Additionally, a tubular projection is formed integrally with one of the housing parts to form part of a Faraday cage for shielding an amplifier circuit of the instrument.

Abstract: A method of measuring a radon concentration or a radon exposure level comprising: placing a plurality of individual radon measurement instruments at locations, each instrument being capable of data output; receiving radon measurement data from each of said plurality of instruments; combining said data from said plurality of instruments into a single data set; and calculating a radon concentration or radon exposure value from said single data set. Using a plurality of individual detectors and combining their data provides a much better overall analysis of radon concentration or radon exposure level. The calculated value may include producing an average of the radon concentrations across the multiple instruments. The average may be weighted with weights determined according to e.g. different locations such as proximity to ventilation devices or based on the time that an average user spends in each location.