of urine out of the composting chamber. Alternatively, in rural areas, men and boys may be encouraged just to find a tree. Construction The composting chamber can be constructed above or below ground level. It can be inside a structure or include a separate superstructure. A drainage system removes leachate. Otherwise, excess moisture can cause anaerobic conditions and impede decomposition. Urine diversion can improve compost quality, since urine contains large amounts of ammonia that inhibits microbiological activity. Composting toilets greatly reduce human waste volumes through psychrophilic, thermophilic or mesophilic composting. Keeping the composting chamber insulated and warm protects the composting process from slowing due to low temperatures. Odorous gases The following gases may be emitted during the composting process that takes place in composting toilets: hydrogen sulfide (H2S), ammonia, nitrous oxide (N2O) and volatile organic compounds (VOCs). These gases can potentially lead to complaints about odours. Some methane may also be present, but it is not odorous. Pathogen removal Waste-derived compost recycles fecal nutrients, but it can carry and spread pathogens if the process of reuse of waste is not done properly. Pathogen destruction rates in composting toilets are usually low, particularly of helminth eggs (such as those from the genus Ascaris). This carries the risk of spreading disease if a proper system management is not in place. Compost from human waste processed under only mesophilic conditions or taken directly from the compost chamber is not safe for food production. High temperatures or long composting times are required to kill helminth eggs, the hardiest of all pathogens. Helminth infections are common in many developing countries. In thermophilic composting bacteria that thrive at temperatures of oxidize (break down) waste into its components, some of which are consumed in the process, reducing volume and eliminating potential pathogens. To destroy pathogens, thermophilic composting must heat the compost pile sufficiently, or enough time (1–2 years) must elapse since fresh material was added that biological activity has had the same pathogen removal effect. One guideline claims that pathogen levels are reduced to a safe level by thermophilic composting at temperatures of 55 °C for at least two weeks or at 60 °C for one week. An alternative guideline claims that complete pathogen destruction may be achieved already if the entire compost heap reaches a temperature of for one hour, for one day, for one week or for one month, although others regard this as overly