Human body Humidity, relative

The comfort of the human body depends primarily on tiuee environmental factors the temperature, relative humidity, and air molion. Tlie temperature of the environment is [he single most important index, of comfort. 

C What is latent heat How is the latent heat loss from the human body affected by (a) skin wetledness and (b) relative humidity of the environment How is the rale of evaporation from the body related to the rate of latent heat loss ... 

Heat comfort is affected by six factors which are four environmental parameters including dry bulb temperature, relative humidity of air, wind velocity and average radiant temperature, and two anthropometric parameters including activity intensity of human body and heat-resistance of clothes, which has been proved by lots of researches (Fanger P O et al. 1974, Zeng G et al. 2007, Wang S G et al. 2010). 

As the human body is homeothermic, heat production from the body should ideally equal heat loss. The metabolic rate can vary from about 80 W at rest up to over 1000 W during most strenuous activities, and a large part of this power is converted into heat (typically 80-85%). If the heat production is high, the largest part of this heat has to be evacuated to the environment. The heat exchange with the environment depends on four environmental factors the air temperature, the radiant temperature, the relative humidity in the air and the wind speed. Heat transfer can occur by four different means ... 

Heat Index The heat index has come into common use. During the heat of the summer, most local weather reports include the heat index along with the actual dry-bulb temperature. Another name for the heat index is the apparent temperature. It represents what the temperature feels like to the human body when air temperature combines with relative humidity. 

The occupational environment can be neutral, cold or hot. A combined action between the four environmental parameters (temperature, relative humidity, velocity and radiant heat) and the two individual parameters (clothing worn by the occupants and their activity) can lead to a thermal comfort, discomfort, or to a thermal stress situation (Parsons, 2013). The integration of these parameters can be done in a thermal index in a way that will provide a single value that is related to the effects on the occupants. Three types of indices can be identified empirical, rational and derived. According to Parsons (2000), rational indices are derived from mathematical models that describe the behavior of the human body in thermal environments. The analysis of these situations can be achieved using diverse techniques and comfort models, such as Computation Fluid Dynamics (CFD) and other numerical simulations (Murakami et ah, 2000). The human thermal software (Teixeira et al., 2010) is based on differential... 

C05-0098. In the tropics, water will condense in human lungs when the temperature and relative humidity are too high. Using Table 5-4. estimate the vapor pressure of water at body temperature of 37 °C. If atmospheric temperature is 40 °C, at what relative humidity does this life-threatening process... 

However, at whole-body exposures at elevated temperatures (i.e., 95°F) and 35-97% relative humidity, the time to incapacitation was shortened. McNamara et al. reported that men may work without any signs of discomfort in an atmosphere where CS gradually accumulates, whereas these concentrations were intolerable to individuals entering the contaminated area from unexposed areas. Thus, it appears that adaptation develops gradually as the CS concentration increases. When the tolerant individual left the contaminated area for short periods of 10 to 30 min, the tolerance was lost, and re-entry into the contaminated areas resulted in intolerable irritation. Moreover, additional studies on human volunteers have documented the development of tolerance to CS. " ... 

---