Humidity levels

Finishing sprays and spritzes are sprayed on clean, dry hair and tested for drying time, stiffness, combing ease, flaking after combing and stickiness upon contact with moisture. Additionally, hair hoi ding properties are evaluated by measurements of the cud retention at various humidities. Standardized water-set cuds are sprayed with standard amounts of product under controlled circumstances. They are then dried, placed into vadous humidity levels, and the cud fall monitored at vadous time pedods. 

In neutral and alkaline environments, the magnesium hydroxide product can form a surface film which offers considerable protection to the pure metal or its common alloys. Electron diffraction studies of the film formed ia humid air iadicate that it is amorphous, with the oxidation rate reported to be less than 0.01 /rni/yr. If the humidity level is sufficiently high, so that condensation occurs on the surface of the sample, the amorphous film is found to contain at least some crystalline magnesium hydroxide (bmcite). The crystalline magnesium hydroxide is also protective ia deionized water at room temperature. The aeration of the water has Httie or no measurable effect on the corrosion resistance. However, as the water temperature is iacreased to 100°C, the protective capacity of the film begias to erode, particularly ia the presence of certain cathodic contaminants ia either the metal or the water (121,122). 

Table 8 indicates the compatibiUty of magnesium with a variety of chemicals and common substances. Because the presence of even small amounts of impurities in a chemical substance may result in significantly altered performance, a positive response in the table only means that tests under the actual service conditions are warranted (132). Other factors which may significantly alter magnesium compatibiUty include the presence of galvanic couples, variations in operating temperatures, alloy composition, or humidity levels. 

Finally, other properties of asbestos fibers may be evaluated depending on the envisaged appHcation. Typically, the grits and spicule content, the magnetic susceptibiUty (magnetic rating), the content in soluble chlorides, and the humidity level may be of a particular interest in specific appHcations. 

Environmental operating conditions. This will include such factors as operating temperatures, including duration of use at elevated temperatures, presence of water, solvents, oils and chemicals which may be reactive with the plastics materials (not just the polymer but also with the additives) and expected humidity levels. 

Comfort is reduced by elevated humidity levels. It is recommended that on the warm side of the comfort zone the relative humidity should not exceed 60% to prevent warm discomfort. On the cool side of the comfort zone, high humidity is less important because there is no swearing to increase skin moisture. For these reasons the upper boundaries of comfort zones in Fig. 5.7b are wet bulb temperatures of 18 and 20 °C for the winter and summer comfort zones respectively. 

Control of the indoor cooled condition will be by thermostat in the return airstream, and thus based on room dry bulb temperature. The resulting humidity level will depend on coil characteristics and air flow. Packaged air-conditioners for tropical applications commonly have a design coil sensible/total ratio in the order of 0.7 with entering air at 50% saturation, and will give indoor conditions nearer 45% saturation if used in temperature climates with less latent load (see Chapter 35). 

The use of direct steam injection into air is a common method of increasing humidity levels for both commercial and industrial applications. The process kills most types of bacteria and similar organisms that may contribute to fouling, health, or other indoor air quality (IAQ) problems. Where amines are present in the steam, however, even small concentrations can be detected by their odor and may be objectionable, even though they may be well under guidelines for concentrations in air. 

Toronto is located on the northern shore of Lake Ontario. The high average monthly maximum temperature occurs in July at 26.5 °C with an extreme historical high of 40.6 °C. Relative humidity levels of greater than 80% often accompany the maximum temperatures and determine the low chilled water temperatures needed for dehumidification. The mean daily temperature averaged over the year is 8.9 °C. 

The hydrocarbon membrane can also operate at higher temperatures, of up to 95°C, which allows the use of smaller radiators to dissipate heat. It also lasts 50% longer, while generating up to 15% more power and operating at lower humidity levels. Fluorocarbon membranes can cost about 300 per square meter, the PolyFuel materials cost about half of this. While hydrocarbon membranes may have to prove themselves to many, Honda s FCX fuel cell cars use them. 

An industrial standard method has been developed to test the lightfastness of polymers in accelerated test equipment [103]. The apparatus consists of a quartz-xenon tube with a special optical filter between the light source and the specimen to produce light that resembles window glass-filtered daylight [104], Samples are mounted at a specific distance from the arc and are supported on a frame which revolves around the arc 1 to 5 times per minute for uniform exposure. A blower unit in the base provides a flow of air which makes it possible to maintain a black panel temperature of 45°C, measured by a black panel thermometer which is positioned at level with the samples. A black panel unit consists of a bimetallic thermometer mounted on a steel frame. Both faces of the frame plate and also the stem of the thermometer are coated with a heat-resistant glossy black enamel. The relative humidity level in the exposure cabinet is closely controlled. 

The chemical product used in the design project (chapter 12) is a household appliance designed to deliver clean air by removing and killing airborne microorganisms, and converting carbon monoxide and common VOCs found indoor into harmless carbon dioxide and water. It also dehumidifies indoor air and maintains a comfortable humidity level that suppresses fungal proliferation. The appliance is intended to maintain its performance without maintenance for at least two years and is expected to have a functional life of at least five years. The product contains an active formulation of (1) low temperature oxidation catalyst, (2) VOCs adsorbent and (c) desiccant. 

There is a strong driving force towards operation at higher temperatures and lower humidity levels it will make the fuel cell system simpler, heat transfer from the fuel cell will become easier, and tolerance towards impurities will improve [70], Operation for automotive applications is targeted towards 120 °C, while stationary systems could be operated at even 150 °C and higher. The key component needed to enable this higher operating temperature is the electro-... 

As in aquatic applications, weathering and hydrolysis are the dominant degradation mechanisms for terrestrial applications. Polymer articles covered with dirt can be problematic since photodegradation is not available however, the higher humidity levels and microbial activity in the soil when compared to the atmosphere are advantageous for degradation. 

In order to assess the dependence of the output signal on changes in the humidity content of the sample gas, an additional series of measurements was carried out. The hotplate temperature was set to 275 °C, and CO measurements were recorded at three different humidity levels (10, 20 and 40% r.h.) The humidifier temperature was set to 23 °C, and the chip temperature was 30 °C. As can be seen in Fig. 5.14, the sensor response increases with increasing humidity. The large sensor response difference between 10% and 20% r.h. shows that this effect is more pronounced at low humid-... 

Fig.5.14. Sensor responses, AS, versus CO concentration at different humidity levels (10-40%)...

Transport properties of hydrated PFSA membranes strongly depend on nanophase-segregated morphology, water content, and state of water. In an operational fuel cell, these characteristics are indirectly determined by the humidity level of the reactant streams and Faradaic current densities generated in electrodes, as well as the transport properhes of catalyst layers, gas diffusion layers, and flow... 

The amounts of water absorbed as function of relative water vapor pressure (relative humidity) for HA and its esters are reported in Tables 1-4. HA absorbed the highest amount of water at all humidity levels compared to its esters. The ethyl ester (Hyaff ) absorbs more water than the other two, and the dodecyl ester (Hyaff73) absorbs more water than the benzyl ester (Hyaffll). A small percentage of water absorption hysteresis, between sorption and desorption, was found for the four different materials analyzed. No significant differences in the percentage of hysteresis was found among the HA and the three esters. 

Apparently, a systematical search is necessary to obtain a robust TLC separation. Therefore the complete mixture design space was scanned with a resolution of 4%. For each of these solvent compositions the minimum resolutions and peak orders were calculated for 121 different temperature/relative humidity combinations (11 temperature and 11 relative humidity levels). Based on these 121 resolutions the lowest and the average minimum resolution were estimated. The number of different spot orders was calculated. Besides that, a region of special interest was designated. This region had as upper boundaries 25 °C and 60% RH Within this region the same values were estimated. 

To extend the shelf life of explosives contg NH4N03, it is important to minimize its hygroscopicity. Samples.were tested for hygroscopicity at relative humidity levels of 60, 70, 80 90%... 

For optimum efficiency, humidity levels, temperature, and pressure should be monitored and controlled during the adsorption. The adsorption process of VOCs removal is exothermic in the most cases, which should be considered as a significant design parameter, since there is a risk of fire in the removal of high loads of organic compounds that exhibit high heats of adsorption. 

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