North American Waste Anesthetic Gas Disposal (WAGD) designers have largely come to share this common set of assumptions:
1. Dumping the WAGD into the medical vacuum source is cheap. This is assumed to be true in equipment terms and also in the designer's own time - no line sizing or pump sizing needs to be done other than what must be done for the vacuum anyway.
2. In a Dual use implementation, any oxygen or other gases will arrive at the pump sufficiently diluted to render them harmless.
3. Any other problem will be handled by someone else. These assumptions have lead to the most common implementation of WAGD in North America today - a WAGD terminal at each anesthetizing location piped into the medical vacuum line and thence into the medical vacuum pump.
Two unexpected consequences are being reported:
1. Fires in vacuum pumps. We had no verifiable reports of fires in WAGD pumps for many years. But beginning in the last half of 2002 and continuing through today, there have been reports of pump fires. The reports range from flashes at the exhaust through to complete explosive destruction of pumps. In all the cases corroborated so far, the pumps were in dual use WAGD and medical vacuum service, and all were oil lubricated.
2. Vacuum pumps running excessively. In numerous cases both with vacuum pumps in Dual use service and in dedicated WAGD service, pumps have been seen to be running much harder than expected or than that same pump had run historically. In extreme cases, this has resulted in pump failure.