A controller as a CO.sub.2 sensor reference value calibration apparatus calibrates a reference value of the CO.sub.2 sensor in the following manner. Introduction of outside air is started after a person is not detected. A CO.sub.2 concentration, which is acquired when a preset first waiting time elapses, is set as a provisional reference value. The carbon dioxide concentration, which is acquired when a preset second waiting time elapses, is compared with the provisional reference value. In a case where a change rate of the carbon dioxide concentration is out of a preset allowable range, the carbon dioxide concentration is acquired when the second waiting time elapses after newly setting the acquired carbon dioxide concentration as the provisional reference value. In a case where the change rate of the carbon dioxide concentration is in the allowable range, the currently set provisional reference value is set as the reference value.

A system and method for concurrently measuring odorant concentration and also compensating for changes in relative air density when measuring odor intensity levels may be used to provide more accurate and reliable readings from an odorometer. Odorometers typically measure the concentration of a given target gas in a gas-air mixture. Because changes in air density make it difficult to accurately determine how much air is in the gas-air mixture sample, a method of compensating for changes in the air density is able to produce a more accurate concentration reading. By measuring the relative temperature and pressure of the air at calibration and when a particular reading is taken, the final reading can be corrected to account for changes in the air density. By correlating the odor intensity readings with odorant concentration readings a wide array of advantages may be realized.

An online gas chromatograph is provided. The online gas chromatograph includes a sample inlet and at least one chromatographic column operably coupled to the sample inlet. At least one valve is interposed between the sample inlet and the at least one chromatographic column. A detector is fluidically coupled to the at least one chromatographic column. A controller is coupled to the detector and to the at least one valve, the controller is configured to control flow from the sample inlet through the chromatograph using the at least one valve. The controller is configured to generate a plurality of sequential calibration cycles, where each calibration cycle has a calibration gas purge operation. The first calibration gas purge operation lasts longer than the second calibration gas purge operation.

A gas sensing device is adapted to detect a concentration of a target gas. The gas sensing device comprises a dielectric layer, a reference sensing portion, a target sensing portion, and a controller. The dielectric layer is disposed on a surface. The reference sensing portion and the target sensing portion are respectively disposed on a supporting side of the dielectric layer, with said supporting side facing away from the surface. The reference sensing portion includes a first conductive layer and a first sensing layer with low sensitivity to the target gas. The target sensing portion includes a second conductive layer and a second sensing layer with high sensitivity to the target gas. The controller obtains the immittance values of the first conductive layer and the second conductive layer, and calculates a concentration value of the target gas according to the immittance values and a correlation function.

The described sensor allows determination of the concentration of a gas in a two-component mixture at variable pressure by measuring the diffusivity and the thermal conductivity. The sensor is provided to alternately heat the membrane of a thermally conductive cell and allow it to cool such that the temperature T.sub.M of the membrane passes from a first stable value to a second stable value and vice versa via a transient mode. The cell produces a signal representative of the temperature T.sub.M of the membrane and the sensor extracts from the signal a first and a second parameter that respectively relate to said first stable value and said transient mode of the signal. A value of the concentration of said gas and of the pressure of said two-mixture is calculated from these two parameters.

A device and method for calibrating a NO delivery device using NO and NO.sub.2 measurements, without using a known standard.

A mobile environmental sensor system includes a first mobile environmental sensor, a controller, and a network transmitter disposed on a transport unit. The controller is in electronic communication with the first mobile environmental sensor and the network transmitter. The controller includes a processor and a memory. The processor is configured to trigger a measurement from the first mobile environmental sensor. A sensed value is received from the first mobile environmental sensor. The processor compares the sensed value as received from the first mobile environmental sensor to a reference sensed value received by the controller via the network transmitter. The processor calibrates the first mobile environmental sensor based on the comparison of the sensed value as received and the reference sensed value as received. The calibration includes a normalization between the sensed value as received and the reference sensed value as received. The normalization includes a time dependent component.

A portable gas detecting and monitoring apparatus includes a case having a continuous sidewall including a first end closed a first end cap, and a second end closed by a second end cap connected sealably and removably to the continuous sidewall. The continuous sidewall is triangular between the closed end and the open having three sides and three corners, two of the three sides being straight and equal in length, one of the three sides being rounded, and each of the three corners being rounded. A gas detection and monitoring unit mounted in the case includes gas, pressure, and temperature and humidity sensors in communication with an ambient atmosphere outside the case, a data processor operatively connected to the sensors, data storage, an information display viewable through the case, and a calibration unit for calibrating the gas sensor to a predetermined gas concentration measured by the gas sensor.

Embodiments of the present disclosure provide for dynamic iterative baseline adjustment. Such embodiments provide improvements to sensors requiring such adjustments, for example by better accounting for baseline drift and/or other baseline inaccuracies of a sensor. In one example context, a gas sensor is provided that performs such dynamic iterative baseline adjustment to better calibrate the output value of the gas sensor. Some embodiments include determining a set of measured values comprises a number of low-point measured values that exceeds a baseline updating threshold, determining an updated baseline value set, for example by determining an average low-point measured value for each baseline factor interval of a set of baseline factor intervals, and updating the baseline value set to the updated baseline value set, and optionally performing a corrective baseline algorithm on the updated baseline value set. The updated baseline value set may be utilized to correct subsequently measured raw data values.

A gas phase standard preparation device and method of use for creating a final reference material is disclosed. The final reference material is used to quantitate certain gaseous compounds in collected air samples. This is accomplished by providing a sealed ampule tube with an ampule containing reference material that is eventually breached by the gas preparation device. Once the ampule is breached, the reference material within the ampule is blended with a diluent gas and forced into a reference material cylinder. The concentration of the final reference material within the reference material cylinder can then be verified for use in testing collected air samples. Accordingly, this device allows for creating a custom final reference material onsite in a laboratory without the need for shipping in pre-made compressed gas cylinders for air quality testing.