Smoke Ejectors & Positive Pressure Ventilation
One of the many things we deal with on a fire scene is smoke and dangerous fumes. Many times on a service call there may not be any flames at all, just a lingering smoke in the air. For a variety of reasons we find ourselves needing to vent areas. There are two types of ventilation, horizontal or vertical. Here we will be focusing on horizontal.
Horizontal ventilation is accomplished with two main tools, smoke ejectors and positive pressure fans. Although there are other means to vent a building horizontally (Such as hydraulically through a fog pattern) those will be covered elsewhere.
The images to the right show the tools used in standard horizontal ventilation.
The top image is a typical smoke ejector. This device requires typical household or generator electrical power to operate and works on a negative pressure principle. It is typically set in a doorway or window and can also be hung using the hanger shown in the middle picture. This fan pulls the air from the structure. This fan is most useful for small fires, burnt food, etc. You simply put it in place, plug it in and turn it on.
The bottom picture shows a positive pressure fan. These are typically gasoline powered (Although not always). A positive pressure fan is setup a set distance outside of a door or window so that the cone of air it is pushing covers the entire opening. This fan then pressurizes the structure forcing the smoke and fumes out an opening on the other side. Two important things to remember: 1) This works best when the opening you are pushing air through is approximate in size to the opening on the other side. 2) In order for this to work we can't be breaking every window we see. This relies on the fans ability to pressurize a house or dwelling, and that can't be done if we've broken all the windows or doors. Click HERE to see a video.