What precautions must be used when using fuels and gases in the subway system?

Using portable containers of up to 2.5 gallons is a precaution that aligns with safety regulations in environments like subway systems where flammable materials are present. This limit is intended to minimize the risk of fire and explosion, as larger quantities of fuel can pose significant hazards in confined and populated areas, such as a subway. Smaller portable containers can be more easily managed and controlled, reducing the chances of spillage or accidental ignition.

The use of portable containers also simplifies transportation within the system while ensuring that they are handled correctly. This is particularly important because enclosed spaces like subways have limited ventilation, making the presence of flammable gases and fuels particularly dangerous. By regulating the size of the containers, safety protocols ensure that workers can operate within safer parameters, reducing overall risk to both the workers and the public.

In contrast, options suggesting that only large tanks or storing gases in permanent facilities are acceptable do not prioritize the immediate safety of workers and the environment. Similarly, stating that no specific precautions are necessary disregards the inherent risks associated with handling fuels and gases, particularly in the unique context of subway systems.