Exposure chamber environment control

Kerr, H. D. Diurnal variation of respiratory function independent of air quality. Experience with an environmentally controlled exposure chamber for human subjects. Arch. Environ. Health 26 144-152, 1973. 

Human volunteers have been exposed to SM vapour, either whole body or on selected regions of the body, normally the arm. In addition, whole body exposures have been undertaken in a controlled chamber environment and in the field, under a variety of climatic conditions. Exposures in chambers are more accurate, because, although the field trials may have used vapour capture devices to sample the air, the variation in vapour concentration during the exposure could not be accounted for. 

A survey of the environmental control and monitoring technology used in several experimental studies indicated significant limitations in experimental control capability. There are seven controlled-environment chambers or clean-room facilities in the United States for human exposure (community air pollution inhalation) from which studies have been reported. Another is under construction at the University of North Carolina in association with the epa at Chapel Hill. There are three chambers in Canada of similar design. 

In one study,human subjects were tested in a controlled-environ-ment chamber with a high (summer) temperature and with ozone, nitrogen dioxide, and carbon monoxide as pollutants. Performance on a divided-attention task given at the end of the exposure period and the subjects heartrate variability (a potential psychophysiologic measure of attention) were evaluated. The subjects displayed a significant decrement in peripheral attention associated with increased ambient temperature. Effects attributable to pollutant gases were variable. 

Figure Test chamber for the dynamic mechanical moisture sorp-tlon/desorptlon experiments The design of this chamber enables exposure of the sample to a variety of liquid and/or vapor environments. Temperature of the chamber can be controlled by adjusting flow or temperature In the liquid or gas supply lines. Alternatively, the chamber can be jacketed with cooling water or heat tape.

Controlled exposure studies of volunteers in stainless steel chambers have been performed. Most have involved exposure to one specific mixture of VOCs for example, the work of Molhave and Nielsen in 1992. These studies consistently document relationships between symptoms and increasing exposure levels. Office workers who perceived themselves as susceptible to the effects of usual levels of VOCs indoors demonstrated some impairment on standard tests of neuropsychological performance. Healthy volunteers, on the other hand, demonstrated mucous membrane irritation and headaches at exposures in the range of 10-25mgm but no changes on neuropsychological performance. Recently, office workers demonstrated similar symptoms after simulated work in environments where pollutants were... 

Simultaneous plant exposure to the aerosols and control environment - efforts were made to minimize individual plant differegces which may be apparent even in clonally propagated species. Chambers were designed to allow simultaneous, yet separate, exposure of different branches of the same plant to aerosol and control environments where appropriate, this system also allowed whole plant exposure. 

The process of adsorbate deposition should be carried out in a well-controlled environment. UHV is ideal in storing the surfaces and is indispensable for handling clean Si surfaces of Si. UHV chambers and tubings are convenient for most heating and gas exposure treatments. H Si(lll) and organic-modified Si surfaces are... 

Upon subsequent exposure to ambient environments in several humidity and temperature-controlled chambers these curvatures varied with time due to the two aforementioned contradictory time-dependent mechanisms. While the time-dependent moisture diffusion process serves as a stress-inducing mechanism, the time-dependent relaxation acts to reduce the level of those stresses. Note that relaxation depends on moisture content through the shift factor an m). 

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