Final answer:
A foam tender pressurizes its two 350lb dry chem Purple K systems using pressurized nitrogen or air, which enables the fire suppressant to be deployed rapidly and effectively against flammable liquids and electrical fires.
Step-by-step explanation:
In the context of fire-fighting equipment, a foam tender is a specialized vehicle that supplies large amounts of foam to fight fires involving flammable liquids and hazardous materials. The pressurization of the two 350lb dry chemical Purple K systems, typically used in such vehicles, is achieved through the use of pressurized nitrogen or air. These gases force the Purple K powder out of the canister when the system is activated, allowing the dry chemical to effectively suppress the fire.
Purple K, also known as potassium bicarbonate, is particularly effective against Class B and C fires, which involve flammable liquids and gases, and electrical fires respectively. The pressurizing gas is maintained in the system's cylinders, often at pressures around 150 to 200 psi, which allows for the rapid discharge of the fire suppressant when needed.