The density of dust in a tunnel during construction is one of the most important factors among the environmental conditions experienced by construction workers. Dust is caused by blasting, shotcrete, waste-handling, etc. Effectively controlling dust is very difficult, especially during blasting. Thus, an effectively designed ventilation system is needed in order to reduce the density of dust. The behavior of dust in a tunnel is only experimentally understood, but there remain many conditions which affect the efficiency of ventilation. If the behavior of dust in a tunnel could be better understood, ventilation systems would be more effectively designed.