In many applications steam alone is quite sufficient, giving chemical-free cleaning. However in some cases the use of a specialist chemical, such as a degreaser make the cleaning process faster. Additionally some specialist systems, such as Chewing Gum removal are designed to use steam and chemical in order to efficiently deliver chemical and combine the attributes of both systems to give the most efficient solution.
In any case where a chemical is used the chemical is injected into the steam line, improving its efficiency by pre heating thus requiring less chemical to be used. Because of the pre heating effect chemicals that give of harmful fumes when heated must never be used in Steam Cleaners.
Also, only use chemical in a dedicated machine with a chemical tank built in. Never put chemical in the boiler as this will damage the internal components.