Nowadays, large cities cannot work without public transport. The transportation services undoubtedly have their positives and negatives. The greatest risk in terms of threat to life and health in public transport is the very high concentration of people in a small space. The time intervals when this occurs can be estimated in advance. Subway areas can then serve not only to transport people but also hazardous chemicals. The underground railway occupies a leading position in the number of passengers transported not only in Prague. At the present time, chemical terrorism is a serious threat to the security of mankind all over the world and its scale essentially exceeds the impact of use of the most modern firearms.
The article focuses on the issue of spreading of toxic substances in subways and related population protection. The aim is to describe the main factors (chemical, physical and demographic) affecting spreading of dangerous chemical substances released in subway premises during a chemical attack or accident. Another objective is to determine their impact on passengers and to characterize factors that affect spreading of hazardous chemicals. Results of the performed experiments must always be considered in the context of specific circumstances in which they were carried out. There are a number of specifics that can affect spreading and attainable concentrations of poisoning substances.