In various embodiments, rapid, sensitive detection of molecular hydrogen is achieved by chemically converting hydrogen to water vapor and then detecting the water vapor as a surrogate for the hydrogen. Detection may be enhanced by dampening variation in ambient water vapor and rapidly actively modulating a hydrogen-derived water vapor component. For example, the detector may receive sample gas that includes ambient water vapor and hydrogen, dry the sample gas to dampen variation in the ambient water vapor, divide the sample gas into a chemical conversion flow and a bypass flow, chemically convert hydrogen in the chemical conversion flow to water vapor, alternate between measuring water vapor in the converted chemical conversion flow or the bypass flow to produce a water vapor signal, separate the water vapor signal in the time domain to extract a hydrogen-derived water vapor signal, and output a hydrogen signal based on the hydrogen-derived water vapor signal.

In various embodiments, rapid, sensitive detection of molecular hydrogen is achieved by in a detector that divides sample gas into two flows by dividing the sample gas before dampening variation and converting hydrogen to water vapor at two different points. For example, a detector may receive sample gas that includes ambient water vapor and hydrogen, divide the sample gas into a chemical conversion flow and bypass flow, perform a first chemical conversion of hydrogen in the chemical conversion flow to water vapor, alternate between drying the converted chemical conversion flow or the bypass flow to produce a modulated flow, perform a second chemical conversion of hydrogen in the modulated flow to water vapor, measure water vapor in the converted modulated flow to produce a water vapor signal, separate the water vapor signal in the time domain to extract a hydrogen-derived water vapor signal, and output a hydrogen signal based thereon.

Formaldehyde concentration measurement method and apparatus, and an air purifier. The formaldehyde concentration measurement method includes: determining an initial formaldehyde concentration value measured by a formaldehyde sensor; acquiring temperature information and/or humidity information of an environment surrounding the formaldehyde sensor; determining a formaldehyde concentration compensation value of the formaldehyde sensor according to the temperature information and/or the humidity information; determining a target formaldehyde concentration value of the formaldehyde sensor according to the formaldehyde concentration compensation value and the initial formaldehyde concentration value.

A receiver (10) according to the present disclosure includes: a detection unit (11) including a sensor configured to receive a first optical signal of a wavelength included in an absorption band of water molecules and a second optical signal of a wavelength included in an absorption band of carbon dioxide molecules, a signal processing unit (12) configured to calculate a water vapor concentration and a carbon dioxide concentration from changes of intensities of the first and second optical signals, and a determination unit (13) configured to determine whether or not there is a fire that is caused by alcohol combustion based on the water vapor concentration and the carbon dioxide concentration.

The present invention relates to a composite having the ability to stably and reliably detect a target gas even in a moist environment. The composite of the present invention includes: a nanostructure of an oxide semiconductor selected from the group consisting of SnO.sub.2, ZnO, WO.sub.3, NiO, and In.sub.2O.sub.3; and a CeO.sub.2 additive loaded on the nanostructure. The oxide semiconductor nanostructure is uniformly loaded with CeO.sub.2. The composite of the present invention can rapidly detect an analyte gas with high gas response irrespective of the presence and concentration of moisture. The present invention also relates to methods for preparing the composite, a gas sensor including the composite as a material for a gas sensing layer, and a method for fabricating the gas sensor.

Methods and systems for detecting and limiting the water in a photoionization detector are provided. The method may include powering off a lamp configured to ionize particles of air. The method may also include monitoring a signal from the photoionization detector. The signal may be monitored based on a current between a signal electrode and a bias electrode. In an instance the signal is above a signal threshold, the method may also include electrolyzing one or more particles of water present in the photoionization detector by closing a leakage switch in order to allow current to flow through the bias electrode and the signal electrode. In an instance the signal is below the signal threshold, the method may include powering on the lamp to begin photoionization detection. Corresponding systems are also provided.

A gas sensor may include a plurality of elements that are responsive to particular gases based at least in part on the temperature of the temperature sensitive element. A first of the elements may be a gas detection element heated to a temperature at which it is responsive to a gas of interest. A plurality of additional elements may be configured in a reference element network and heated to a temperature at which they are not responsive to the gas of interest but are instead responsive to other effects such as humidity. The reference element network output may be used to remove the other effects (e.g., humidity) from the gas detection element output.

The present invention suppresses an adverse effect caused when an additional gas such as water vapor is mixed in a sample gas or the like that is subjected to gas measurement. In an embodiment of the present invention, in gas measurement for analyzing sensor output signals obtained by alternately supplying a sample gas and a reference gas to a sensor element while alternately switching between the sample gas and the reference gas, the sample gas and the reference gas pass through a humidity equilibration device partitioned by a water vapor permeable membrane, and then are supplied to the sensor element. As a result, since both gases have substantially the same value of humidity at the time of being supplied to the sensor element, influences of water vapor are substantially cancelled out in signals output from the sensor element by the alternate supply of the sample gas and the reference gas.

In various embodiments, rapid, sensitive detection of molecular hydrogen is achieved by receiving sample gas that includes ambient water vapor and hydrogen, passing the sample gas through a gas dryer, chemically converting hydrogen in the sample gas to water vapor to produce converted sample gas, measuring water vapor in the converted sample gas to produce a water vapor signal, separating the water vapor signal in the time domain into an ambient water vapor signal and a hydrogen-derived water vapor signal, wherein the gas dryer dampens variation in the ambient water vapor signal, and outputting a hydrogen signal that describes molecular hydrogen in the sample gas that is based on the hydrogen-derived water vapor signal.

A sampling arrangement includes a sample concentration element configured to trap at least one analyte of interest by freezing; and a sample release arrangement configured to provide a flow of gas, at room temperature on or around the sample concentration element in order to change the temperature thereof; wherein the sample release arrangement further includes a release gas preprocessing element; and a pump element configured to provide the gas flow on or around the sample concentration element.