Radiant Heat?

[Gallonspermin]

Just doing some reading about exposure protection and it says to hose down the side of the structure you are protecting. To put a stream up between the Fire and the structure is no good because radiant heat passes through water.
Why do companies make special nozzles that put up a water curtin?

[IJHumberson]

This topic would probably be debated about as much as the "fog nozzles vs. straight streams" would.

IMHO, if you've ever been behind a fog nozzle on wide pattern fog and advanced up to a propane tank fire, you KNOW that a fog stream will reduce the radiant heat. The real question is whether or not it will reduce it enough for exposure protection - but that all depends on the intensity of the fire and the distance to the exposure. The "one rule fits all" answer is to put the water on the exposure - that way you know that the exposure will never reach a temp. greater than 212 degrees F (unless you run out of water). For many exposures a fog stream between the fire and the exposure would probably work - but who wants to or needs to worry about that when putting the water on the exposure will get the job done?
It's just like the fog/straight stream debate - both get the job done (put the fire out - or, in this case, protect the exposure) but there are a lot of different opinions on which one is best - and it really boils down to personal preference and the particular conditions at hand. Clear as mud?

[BFD847]

I would have to agree with applying water directly onto the exposure. I have am sure and have experienced the decrease in heat while using a fog stream the problem is unless your raging fire is in a dog house your fog pattern is not going to be large enough to protect exposures from all of the radiant heat. Using 1 3/4" line on straight stream against the exposure also allows your FF team a safer distance from the hot zone.
Just my thoughts.

[DrInferno]

The reason they make these appliances is so they can act as unmanned hoselines. The ones I have seen that are built by fire equipment manufacturers have a swiveling head so that the water curtain can be directed on to the exposure to reduce latent heat build up while allowing firefighters to perform other tasks. The problem is that it is easy to bump the hose and have the water curtain become ineffective.