Types of scavenging system II

Passive systems

Components

1. A collecting and transfer system that consists of a shroud connected to the automatic pressure limiting (APL) valve (or expiratory valve of the ventilator).  A 30 mm connector attached to the transfer tubing leading to the receiving system.

2. A receiving system (reservoir bag) can be used.  Two springloaded valves guard against excessive positive (1000 Pa) or negative (-50 Pa) pressures in the scavenging system.

The waste gases can be ducted out of the building via:

 An open window

 A pipe passing though an outside wall

 An extractor fan vented to the outside air (N.B. not into the building's air-conditioning system)

Advantages

 Inexpensive to set up
 Simple to operate

Disadvantages

 May be impractical in some buildings