As mentioned in another thread, I too need the "Idiot's Guide to HVAC" as this is not my discipline.  I am an instrumentation and controls engineer trying to understand the impact of a client changee on work by those invoved HVAC.  I am at a fabrication yard where English is not the first language so questions here are poorly discussed. I am beginning with the changes that affect controls.  Some require more dampers to permit leaving the air-handler operating while isolating areas.  So, let me start with questions specific to dampers.  Non return dampers appear to work like a check valve.  With the fan running, the velocity lifts the louvers but they close by gravity when the fan stops.  What significant details should I know about other type dampers.  We have the following types:
Fire damper and combination shutoff
shutoff
pressure control  
constant volume
balancing
non return
wathertight shutoff
weather tight shutoff

Here are some types of dampers

Dampers-Automatic or Manual:
Adjustable metal plates installed inside of a duct to restrict, control volume, balance, or by-pass air, as required in an air conditioning system.
Fire Dampers
A normally open damper installed in an air distribution system, designed to close automatically upon the detection of heat, to interrupt migratory air flow, and to restrict the passage of flame. The device has been tested in accordance with a standard for safety by a recognized testing laboratory and is identified by a label, affidavit or listing acceptable to the authority having jurisdiction. (Unless the conditions of approval indicate so they are not rated for closing against moving air streams or for withstanding pressure differentials.) A combination of fire and smoke damper must meet the requirements of both.

A smoke damper is a device to resist the passage of smoke which:
a.    Is arranged to operate automatically and
b.    Is controlled by a smoke detector, and
c.    May be but is not necessarily required to be positioned manually from a remote command station.
A smoke damper may be a fire damper or a damper serving other functions, if its location lends itself to the multiple functions. A combination fire and smoke damper shall meet the requirements of both.

Ceiling Dampers
A specialized form of a heat stop installed in the air distribution portion of a fire-rated floor-ceiling or roof ceiling assembly; the sole purpose of which is to help maintain the fire endurance rating of the assembly.
 
Damper, louver
A damper made-up of several vanes operated by gravity or motor control. This type of damper is generally used to control volume of outside air intake or exhaust to the atmosphere.

Damper, Splitter
A damper used to change air flow from one duct to another.

Mixing Dampers
Dampers used to mix both heating and cooling supply air at point of discharge; as in a room.

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