up procedures are provided with all commer- cial compost toilets. Start-up procedures for home-built models dif- fer with the design, but have common aspects. A foot of dry, loose straw should be placed inside a flat-bottomed vault-type compost- ing unit prior to use. The accumulating mass should be thoroughly stirred at least once per month. If the model is one similar to a two- compartment septic tank, the second compartment should be used after about six months and the material in the first compartment left to mature for another six months before it is removed and buried. Because the balance of carbon-rich and nitrogen-rich materials is critical to proper composting, add about a cup of sawdust, peat moss, dry shredded leaves, or lawn clippings per use to supply additional carbon. To start a compost toilet such as the Clivus Multrum, add a large bag of compost, peat moss, or very rich garden soil. Do not use sterilized potting soil. If you use peat moss without a mixture of soil, allow the peat moss to sit for a few days to absorb moisture. After you pack the peat moss along the bottom of the chamber, add a couple of inches of garden soil or leaf mold on top of it. A carbona- ceous bulking agent should be added after each use, just as with the vault-type toilet. During cold weather, bulking agents such as food scraps, dry lawn clippings, and shredded leaves should decompose rapidly and help maintain the internal temperature at proper levels. Routine maintenance includes inspecting and cleaning vent stacks, fan blades, and screens once per year. The liquid level should be checked and the composting material turned every few months. Proper use means putting in appropriate materials and keeping out inappropriate ones. Some inappropriate materials are cigarettes and ashes, metal, glass and plastic, strong chemicals and cleaning solutions, unshredded newspaper, and hay. Don't add meat scraps, plastic-lined disposable diapers, plastic-lined sanitary napkins, or cat litter. Coffee grounds, grease, egg shells, paper to