Humidity optimum relative range

A dry basement with a drain is an ideal location. If the basement is damp, make it dry with a dehumidifier, available from appliance stores. The optimum relative humidity for a darkroom is between 45% and 50% the ideal temperature is between 68F/20C and 75F/24C. It is often easier to maintain this temperature range in a basement than in other parts of the house. Also, hot and cold water and electrical connections are generally available in a basement. Another advantage is the ease with which a basement can be made light-tight. 

Fibers within or slightly below the optimum moisture range may require some heat to maintain these moisture levels when ginning under high relative humidity conditions. 

Figure 2. Optimum relative humidity range (adapted from [4]).

Influence of Salt Concentration. A series of experiments were performed to determine the influence of the salt concentration on the S02 reaction rate. The salts used were NaCl and NaN03 in concentrations ranging from 1 to 15 mole%. The experiments were carried out at a relative humidity of 54%, and a reactor temperature of 66°C. As can be seen from Figure 9, the conversion increases with increasing concentration of additive until about 10 mole%. After this the curve levels off. The optimum concentration of additive is then about 10 mole% for 1 1 electrolytes like NaCl and NaN03. 

The way the flor film forms, and its thickness, appearance and colour, depend on a variety of factors, mainly for the race S. cerevisiae. Especially influential among the cellar environmental conditions are temperature and moisture. The acceptable temperature range for this yeast race is 15-20°C (Marcilla et al. 1936) and the optimum value 15-17 °C. Ibeas et al. (1997) found a temperature of 22.5 °C to be the threshold above which the frequency of respiratory mutants (rho ), which are unable to form a flor film, rises fo a substantial extent. The relative humidity should be higher than 70%. 

The significance of this model is that it describes the optimal situation for water permeation into the spore and therefore ethylene oxide permeation to its target site as a function of the moisture content of the spore and the relative humidity of the environment during exposure. The rate of microbial inactivation therefore increases (as long as all other factors are held constant) with increased relative humidity during exposure. Kaye and Phillips [4] demonstrated a 33% RH optimum for microbial inactivation as a result of exposure to ethylene oxide. In practical situations it is better to err on the side of too much rather than too little moisture. With industrial-scale ethylene oxide sterilization, humidity levels are usually in the range of 50% to 60% RH. The upper limit is usually dictated by deleterious effects on packaging. 

Good activity control is obtained by plate development in a chamber equilibrated with the vapors of a humidity-controlling solution such as aqueous sulfuric acid or a saturated salt solution. A solution of 50% sulfuric acid will provide a relative humidity of —40%, which has proven optimum for reproducibility. In addition, Hahn-Deinstrop (1993) has tubulated saturated salt solutions that will establish constant relative humidities ranging from 15 to 95% in closed chambers. These solutions can be used by placement in either section of a twin-trough chamber or in the inner portion of a horizontal chamber (Chapter 7). 

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