Vertical Ventilation Diagnostics

Inspection Hole

The inspection hole is a diagnostic tool used by the truck company to assess the roof they are about to encounter.  This cut tells you how many layers of roof material there is and the types.  It also tells you the size of the rafters you will be working on.  These are very important to know when going to the roof.  The hole will never be bigger than your boot.  If it was it could be a dangerous hole for firefighters to fall into.  The first cut is at a 45 degree angle to the bearing wall.  This will be your longest cut because it goes until you find a rafter and roll it.  Then make the other 2 cuts to complete the triangle.  This video is on a pitched roof but it works for flat also.                                                                                                                 

Smoke Indicator Hole

The smoke indicator hole is another diagnostic I use to asses smoke conditions for my egress to my ladder  off the roof.  It has replaced the kerf cut in my eyes because it more accurately will assess smoke conditions.  It is simple just drop the tip of the saw in 3 times creating a triangle.                                         

Kerf Cut

The kerf cut is less effective because if the roof tar starts to melt it will seal off the kerf cut not allowing you to assess the roof conditions or more dangerous lead you to believe conditions are not deteriorating when they are rapidly