The BioTioo is mechanically sealed at rest, without a single component running. Odor control for us is a state of design, not a function that consumes power. Three components create this state: the separation of urine and solids, the SmellX seal on the urine path, and the dry solids chamber. The 12-V fan is the fourth level, modular and included as standard in the RL configuration.
Sealed is a state, not a function
The passive chain works without power, sensors, or moving parts:
- Separation at the source. Urine and solids never come into contact. This prevents the ammonia reaction from starting, which causes the typical toilet odor (the basic principle explains how the dry toilet works).
- SmellX on the urine path. The float ball seals the liquid and air openings of the tank by itself, even when tilted. The construction of the component is shown in The SmellX odor seal.
- Dry solids chamber. Coconut fibers bind residual moisture, the contents dry, and pre-composting begins. Dry material smells like forest soil.
Each of these three barriers holds even with an empty onboard battery. This is exactly what we designed the construction for in Überlingen. Three days of rain in autumn, the solar system barely produces anything, the refrigerator has priority: this situation does not affect the toilet.
Why we don’t tie the concept to a fan
A fan in a toilet can serve two different purposes. In chemical toilets, a continuously running exhaust fan often handles all odor control: it maintains negative pressure in the cassette, air continuously flows outside, and the entire odor concept relies on this. If this fan fails, for example due to an empty battery, the odor control fails with it.
The fan in the BioTioo serves a different purpose: drying the solids container. It speeds up how quickly moisture escapes from pre-composting and thus influences how many uses the container can handle. Odor control itself does not depend on it but on the separation, the SmellX seal (our design decision on the urine path), and the dry chamber—all without power. How this chain overall prevents a dry toilet from smelling is shown in Why a dry toilet doesn’t stink. Whether it runs intermittently or continuously does not change this; both modes are available.
If our battery fails, only the drying stops, not the odor control. The undervoltage protection also switches off the fan before it deeply discharges the battery. What else runs without onboard power, up to the hand crank as a backup for the stirring mechanism, is described in Fully functional without power.
What the 12-V fan does and does not do
This drying precisely influences how many of the 20 to 30 uses the container can handle (why this does not affect the odor issue is explained above). In the RL configuration, the fan is included as standard; in the B or R variants, you can retrofit it. It is especially valuable with full occupancy, summer heat, temperature fluctuations, and in small bathrooms without windows.
The technology is economical: 12 volts, 1 watt, electronically controlled, interval or continuous operation via toggle switch, its own fuse, undervoltage protection. Three connection positions are available for installation, on both sides and at the back.
Two things we honestly say about it. The fan needs an exhaust path to the outside, so a planned hose route through a wall or floor. This air is not dust-dry either; it picks up moisture as it flows through the chamber. A low outlet, for example over the floor, service hatch, or an external cover, lets condensate drain downward. Routing upward through the roof cools the air on the way, leaving condensate standing in the duct without drainage. That’s why we plan the exhaust path low. And the steps of the passive chain remain, with or without a fan: you wipe the separation insert briefly after each use, stir briefly with the compost variant, and prepare fresh coconut fibers every 10 to 14 days. For two people, the 10-liter urine tank is due after about 3 days. A detailed guide to the fan is available at Dry toilet with fan.
Availability
The passive chain is standard on every BioTioo 2.0; the L variants come with the 12-V fan included. For retrofitting, there is the fan kit with 1.5 m hose and optional 90-degree or straight angle; the straight angle also fits toilets from other manufacturers. We offer a 3-year warranty and 60-day return policy on the bowl and lid. All configurations can be found in our dry separation toilets.
