If their brand's labeled "nontoxic," "natural," or "biodegradable," be wary as these labels may not mean much. Remember, manufacturers don't have to list ingredients on the label.
• Find out whether the company is committed to sustainable business practices. In addition to its choice of cleaning products, does the business attempt to reduce its environmental footprint by considering transportation issues and building operations? Does it offset for the carbon emissions it generates?
• Ask what else the business does to define itself as green. Are the employees cognizant of water usage, conserving where possible and using cooler water when it makes sense? Do they clean without electronic appliances? Do they clean with reusable tools - cloth rags instead of paper towels?
If the greenness of the cleaning products is your primary issue, consider sticking with a conventional service and ask that they switch to your cleaning products. Most are happy to use whatever products you specify, whether your homemade recipes or green-brand formulas.