Determination of PMV and PPD Indices for Moderate Thermal Environments

Importance of Determination of PMV and PPD Indices for Moderate Thermal Environments

Occupational hygiene measurements are the measurements that must be carried out by the Environmental Laboratories authorized by İSGÜM with the methods determined by İSGÜM. One of these measurements is “Determination of PMV and PPD Indices for Moderate Thermal Environments”.

Determination of PMV and PPD Indices for Moderate Thermal Environments is carried out within the scope of TS EN ISO 7730 and TS EN 7243 standards. Within the scope of the “Regulation on Health and Safety Measures to be Taken in Workplace Buildings and Annexes”, it is also emphasized that TS EN 7243 standard should be used in the evaluation of Ambient Temperature.

What is PMV (Predicted Mean Vote)?

PMV is an indicator that expresses the temperature level that a group of people feel in a given thermal environment with a 7-digit scale. This scale was developed to measure the subjective perception of thermal comfort and is ranked as follows:

• +3: Very hot
• +2: Hot
• +1: Slightly warm
• 0: Neutral (thermal comfort)
• -1: Slightly cold
• -2: Cold
• -3: Very cold

The PMV value is calculated based on the following factors that influence an individual's thermal perception:

1. Environmental Factors
• Air temperature
• Radiant heat (heat from surrounding surfaces)
• Air flow velocity
• Relative humidity
2. Personal Factors:
• Metabolic rate (the activity level of the person)
• Thermal resistance (thermal insulation capacity of the clothing worn, expressed by the clo value)

Calculation of PMV

PMV is based on a complex mathematical model of the physical environmental conditions and the physiological characteristics of the individual. The PMV value should be close to zero in an ideal environment, because in this case individuals feel neither hot nor cold.

Within the scope of the measurements to be carried out according to TS EN ISO 7730 standard, PMV, i.e. Predicted Average Vote and PPD, i.e. Personal Dissatisfaction Percentage values obtained by percentage ratio to PMV value are obtained. As a result of the measurements made according to TS EN ISO 7730 standard, if the PMV value is between -2 and +2 values, the environment can be considered as mild. If it is above +2, it is necessary to measure WGBT, i.e. Wet Chamber Sphere Temperature, within the scope of TS EN 7243 standard.

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