Understanding Hygrothermal Comfort: Measurement, Impacts, and Optimal Conditions

Posted on Sep 4, 2024 in Biology

Hygrothermal Comfort: A Key Factor in Living Conditions

Definition of Hygrothermal

Hygrothermal refers to the combined effects of humidity and temperature.

Air Humidity

Humidity is the amount of water vapor present in the air.

Measuring Humidity

There are three ways to measure humidity:

  • Absolute humidity
  • Relative humidity: The ratio of actual water vapor in the air to the maximum amount it can hold at that temperature.
  • Specific humidity

A hygrometer is used to measure humidity.

Relationship Between Humidity and Temperature

Air humidity and air temperature have a strong inverse relationship. As temperature increases, humidity decreases.

  • At 20°C, air reaches saturation, holding a maximum of 17.3 g/m3 of water vapor. This equates to 100% relative humidity.
  • 50% humidity indicates that the air contains half the maximum possible water vapor at a given temperature.
  • An optimal indoor relative humidity range is 40-60%.

Impacts of High Humidity

High humidity combined with high ambient temperature can lead to heat stroke. When air humidity is high, the pressure of water vapor in the air nears the pressure of sweat on the skin (around 40 mmHg). This prevents sweat evaporation, leading to:

  • Ineffective body cooling and potential dehydration.
  • Impaired air quality, often described as “stale” or “sultry,” promoting fungal growth.

Impacts of Low Humidity

Excessively low humidity can cause:

  • Drying of mucous membranes.
  • Impaired pulmonary clearance.
  • Increased electrostatic charge in certain materials.
  • Dehydration and heat exhaustion when combined with high temperatures.

Temperature

Individuals have unique temperature comfort zones, influenced by factors like air humidity.

Impacts of Extreme Temperatures

  • Unprotected exposure to extreme temperatures can have severe, even irreversible, health consequences.

Thermal Comfort

Thermal comfort is the feeling of satisfaction with the indoor climate, whether at home or work. It’s achieved when the body’s thermoregulation process is balanced.

Factors Influencing Thermal Comfort

Thermal comfort is influenced by:

  • Indoor climate parameters: Air temperature, humidity, velocity, and heat radiation.
  • Individual characteristics, activity level, and clothing, particularly relevant in occupational settings.

Recommended Microclimate Parameters for Occupational Settings

To achieve thermal comfort at work, recommended microclimate parameters include:

  • Indoor temperature: 20-24°C in winter, 23-26°C in summer.
  • Relative humidity: 40-65%.
  • Indoor air velocity: Less than 0.2 m/s in winter, less than 0.3 m/s in summer.

Health Risks from Excessive Heat Exposure

Excessive heat exposure can lead to:

  • Heat cramps: Caused by salt loss from excessive sweating.
  • Heat exhaustion: A circulatory disorder caused by dehydration, potentially progressing to heat stroke.
  • Heat stroke (hyperthermia, sunstroke): A life-threatening condition occurring when the body absorbs more heat than it can dissipate, leading to thermoregulation failure, shock, organ damage, and potentially death. Symptoms include confusion, headaches, low blood pressure, fainting, dizziness, pale or bluish skin, chills, trembling, and convulsions in children.

Health Risks from Cold Exposure

Exposure to cold can cause:

  • Frostbite: Damage to skin and underlying tissues in extremities (fingers, nose, ears) due to impaired circulation.
  • Hypothermia: A dangerous drop in core body temperature, impairing physiological functions. Symptoms include ataxia, confusion, cold skin, gray complexion, peripheral cyanosis, shivering, tremor, weakness, rapid breathing and heart rate, eventually slowing and weakening, potentially leading to death.

Measuring Temperature and Humidity

Monitoring temperature and humidity is crucial for maintaining a safe and comfortable environment and preventing health risks.

Types of Measuring Instruments

  • Thermometers: Measure temperature to ensure it stays within safe limits.
  • Hygrometers: Measure humidity to prevent issues associated with both high and low levels.
  • Thermo-Hygrometers: Simultaneously record temperature and humidity on a line chart, providing a visual representation of fluctuations over time. These instruments are commonly used in settings like laboratories, museums, and storage facilities where monitoring both parameters is essential.