Physics

Meteorology

Mechanics

Operating system

Airflow

Engineering

Composite material

Ventilation (architecture)

Materials science

Thermal manikin

Inhalation

Layer (electronics)

Breathing

Computer science

Exhalation

Transient (computer programming)

Environmental science

Anesthesia

Simulation

Thermal insulation

Medicine

Mechanical engineering

Indoor Air

The breathing zone of an individual indoors is usually defined as a finite region steadily formed in front of a face. Assuming the steady formation of the breathing zone, we propose a procedure for quantitatively identifying a breathing zone formed in front of a human face in the transient condition. This assumption is reasonable considering that the ventilation time scale of human respiration is sufficiently short compared to the ventilation time scale of a room. We used steady-state computational fluid dynamics (CFD) and a computationally simulated person (CSP). We present the probabilistic size of the breathing zone for various postures and breathing conditions. By analyzing unsteady inhalation and exhalation airflow characteristics via a CSP with a respiratory system, we also estimated the direct re-inhalation rate of the exhaled air. The results can be used for developing methods to control the long-term and low-contaminant concentration exposures.

Breathing zone and exhaled air re‐inhalation rate under transient conditions assessed with a computer‐simulated person