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The representation is made on a temperature-relative humidity, instead of a standard psychrometric chart. The comfort zone in blue represents the 90% of acceptability, which means the conditions between -0.5 and +0.5 PMV, or PPD < 10%.
For humidity ratios above 0.012 kg H 2 O/kg dry air (0.012 lb H 2 O/lb dry air), or for metabolic rates up to 2.0 met, the analytical model must be used to determine thermal comfort sensation. Also based on the PMV model, this method uses tools such as the ASHRAE Thermal Comfort Tool or the online CBE Thermal Comfort Tool for ASHRAE 55 [ 2 ] to ...
The recommended level of indoor humidity is in the range of 30–60% in air conditioned buildings, [34] [35] but new standards such as the adaptive model allow lower and higher humidity, depending on the other factors involved in thermal comfort. Recently, the effects of low relative humidity and high air velocity were tested on humans after ...
Indoor relative humidities should be kept above 30% to reduce the likelihood of the occupant's nasal passages drying out, especially in winter. [38] [41] [42] Air conditioning reduces discomfort by reducing not just temperature but humidity as well. Heating cold outdoor air can decrease relative humidity levels indoors to below 30%. [43]
Determining the effect of temperature change on relative humidity: For air of a fixed water composition or moisture ratio, find the starting relative humidity from the intersection of the wet and dry bulb temperature lines. Using the conditions from the previous example, the relative humidity at a different dry bulb temperatures can be found ...
Temperatures lower than 16 °C (61 °F) with humidity above 65% were associated with respiratory hazards including allergies. [13] [14] The WHO's 2018 guidelines give a strong recommendation that a minimum of 18 °C (64 °F) is a "safe and well-balanced indoor temperature to protect the health of general populations during cold seasons".
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The heat index (HI) is an index that combines air temperature and relative humidity, in shaded areas, to posit a human-perceived equivalent temperature, as how hot it would feel if the humidity were some other value in the shade. For example, when the temperature is 32 °C (90 °F) with 70% relative humidity, the heat index is 41 °C (106 °F ...