Carbon indoor detection

Multi-sensor fire detectors provide faster detection with fewer false alarms. These sensors are capable of monitoring the environment for multiple purposes, e.g. carbon monoxide concentration, concentration of flammable gases and indoor air quality, too. 

Recent studies have revealed that carbon tetrachloride is also a common contaminant of indoor air. Typical concentrations in homes in several U.S. cities were about 1 pg/m (0.16 ppb), with some values up to 9 pg/m (1.4 ppb) (Wallace 1986). Concentrations in indoor air were usually higher than in outdoor air, indicating that the source of the carbon tetrachloride was building materials or products (pesticides, cleaning agents) inside the home (Wallace 1986 Wallace et al. 1987). Based on 2,120 indoor air samples in the United States, the average concentration of carbon tetrachloride was 0.4 ppb (2.6 pg/M) (Shah and Heyerdahl 1988). However, the median value was 0 ppb, indicating that carbon tetrachloride was not detected in more than half the samples. 

A nationwide study of indoor air concentrations of 26 VOCs was conducted in Canada in 1991 (Otson, Fellin and Tran, 1994). An OVM-3500 sampler was exposed for 24 h on one occasion in 757 homes. Approximately equal numbers of homes were sampled in each of four seasons. VOCs were extracted with 1.5 ml of carbon disulphide and 26 compounds were determined by GC with a mass selective detector operated in the selected ion monitoring mode. Detection limits were estimated to be in the range 1.6-5.9pg/m3. Mean concentrations of selected compounds are shown in Table 3.2. 

Breath and air collected at sites in and around New York City were measured for carbon disulfide by Phillips (1992). The group tested consisted of four types (male smokers, male nonsmokers, female smokers, and female nonsmokers) with no significant divergence observed among any of the different group types (see Table 5-2). Carbon disulfide was detected in all air and breath samples taken from both indoor air and outdoor locations (see Table 5-3). A general population survey in Italy found low levels of carbon disulfide in the blood of all 208 subjects tested and in the urine of all 1,256 samples taken (Bmgnone et al. 1994). 

The detection of carbon dioxide (CO2) gas has attracted attention in the context of global warming, biological and health-related applications, such as indoor air quality control, process control in fermentation and in the measurement of CO2 concentrations in the exhaled breath of patients with lung and stomach diseases (Machado et aL, 2005 Namjou et aL, 2006 Thorpe et al., 2006 Thorpe et aL, 2008). In medical applications, it can be critical in hospital to monitor the CO2 and Oj concentrations in the circulatory systems of patients with lung diseases. The current technology for CO2 measurement typically uses IR instruments, which can be very expensive and bulky. 

Besides, according to the review of indoor tests of "salt weathering" on concrete, two experimental results were observed showing that sulfate crystallization can be detected in the calcite crystals, the carbonation products of concrete (Fig. 12) and that carbonation could accelerate the concrete damage (Fig. 17). It might be that the efflorescence also occurs after concrete carbonation. 

As in the case of any flammable gas, never use a flame in trying to detect carbon monoxide leaks. Portable detection equipment or the formation of bubbles by a soapy solution applied to a suspected area will indicate leaks. Carbon monoxide alarm detectors must be installed in all indoor areas in which the gas is regularly used in more than small laboratory amounts. Colorimetric sniffer tubes are also utilized for detection of carbon monoxide. Samples of atmospheric air containing carbon monoxide are aspirated through such tubes. 

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