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Aerosol and gaseous emissions are generated in toilets. Drawing exhaust air from the ceiling ensures effective dissemination of airborne contaminants. Why is the exhaust air not drawn from the toilet instead?

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    $\begingroup$ The word toilet in English can be ambiguous - depending on which part of the world one is in. Do you mean the toilet bowl or the room containing the toilet bowel (in some parts of the world referred to as a latrine, bathroom, water closet)? $\endgroup$ – Fred Sep 23 '17 at 16:54
  • $\begingroup$ @Fred what about bog, khazi, big white telephone... etc $\endgroup$ – Solar Mike Sep 23 '17 at 16:57
  • $\begingroup$ See also "spark plugs". $\endgroup$ – Wossname Sep 25 '17 at 14:42
  • $\begingroup$ rotorooter.com/blog/… $\endgroup$ – agentp Sep 25 '17 at 23:51
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  1. it would complicate toilet designs and make toilet bowls more expensive to manufacture
  2. it would require an electrician to install, as well as a plumber, greatly increasing the cost of installation
  3. the exhaust vent would suck in splashed urine and faeces-laden bowl water, turning the outlet pipe and the exhaust fan at the end into a stinking health hazard
  4. sitting on a vented bowl in winter would result in cold air rushing past your genitals
  5. you are conflating emissions and contaminants — bad (but otherwise harmless) smells rise up from toilet bowls, but the nasty bugs are only transmitted by splashing or human activity, so a ceiling exhaust does not help spread contaminants in any meaningful way because it does not generate strong air currents near the bowl
  6. exhaust vents in toilets have nothing to do with sanitation — they exist merely to maintain air quality (i.e. prevent the room from smelling bad)
  7. given that most replacement air will enter the room underneath the door, a vented toilet bowl will simply draw air along the floor — this will make the extraction of warm, smelly air that has risen towards the ceiling difficult, allowing smells to linger and requiring the exhaust fan to run significantly longer to accomplish its task of clearing the air (with a corresponding increase in electricity consumption and failure rate)
  8. if the toilet becomes blocked for whatever reason, the water level in the bowl could rise to the level of the vent and then get sucked directly into the exhaust pipe and down that pipe towards the electric fan at the other end — a scenario that won't end well regardless of what happens next

Having said all of the above, a number of waterless/composting toilets are vented and do work well — so the idea does have merit in certain circumstances.

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    $\begingroup$ It would require an electrician, a plumber and a someone to do sheet metal to install those fixtures. The electrician part isn't necessarily a big deal in commercial construction; since many toilets are electronic flush valves now and require wiring anyways. Having three distinct trades to install a toilet is a huge hassle though. $\endgroup$ – JMac Sep 25 '17 at 19:39
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Because the design of the bowl (assuming a "standard" toilet with flush) is such that it forms an airlock (the U bend) to stop the smell from the drain entering the bathroom.

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  • $\begingroup$ I think the OP is talking about the smell before it gets past the air lock. $\endgroup$ – Olin Lathrop Sep 25 '17 at 12:14
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They do sometimes. Look up long drop toilet. They're used sometimes at Western campsites. The vent is usually painted black. It heats up with solar radiation and causes a strong convection current that really sucks on the cheeks. They're surprising ly effective.

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