Petroleum solvents are the go-to cleaning product used in parts washers. Stored in a settling pan at the bottom of the washer, an electric liquid is absorbed into the solvent to produce clean solvent from around the top of the tank. The latter is then pumped at a low pressure – through a flexible nozzle – to clean the parts. However, petroleum solvents are highly flammable and impossible to dispose of!
That's why many DIYers opt for aqueous cleaner instead of petroleum solvent. These alkaline water-based solutions break down dirt and grime rather than immediately dissolving them like solvent cleaners. However, their real advantage is that they're non-hazardous and non-flammable, thereby leading to a lower management cost as a result.
To sum up, if you clean extremely grimy parts on the daily, then opting for petroleum solvents is the way to go. If not, aqueous-based cleaners produce fewer solvent vapors to protect the worker's health.. The choice is yours!