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Smoke Distribution Box
By Matt Marich

In October of last year our company was hired to enhance the special effects at a local amusement park haunt. One of the scenes involved two stone columns about six feet apart. They were open at the top and a live actor (sacrifice) was tied between them. Following with this ritualistic theme, we decided on a cold fire effect supplied by one fog machine. Cold fire is usually accomplished with a smoke machine and a hidden light source controlled by some sort of a flicker generator. The budget did not allow for more sophisticated flicker circuits so we simply used multiple bulbs with different colored gels. The following outlines the method used to accomplish this effect with a cost outlay of about $60.00, of course this does not include the props or fog machine but it is well worth the time for a small budget show.

Fog Machines
With the growth of the Halloween market many fog machines by various manufacturers are available. Not all are created equal. In order to source this type of effect, the fog machine must be of a type that can supply fog on a continual basis with little re-heat time. Small home foggers cannot keep up with this type of output requirement. If you consider the fact that these high output units are about double the cost but can supply two rooms with a high volume of smoke, it is well worth it. We utilized a Le Maitre unit and it supplied more than the necessary volume.

The box itself is made from a half a sheet of 3/4" plywood. If your unit is to be inside a covered building, use fire retardant MDF (medium density fiberboard), the substrate used for all Formica counters. If you cannot find this at a local Home Improvement outlet, try contacting a cabinet or countertop maker. If the unit is to be used outdoors, try 3/4" Superply or 3/4" Baltic Birch, as these materials have a fire retardant rating. I suggest sealing the outside of this unit with water based exterior clear coat to avoid warping.

Two small 120 volt 4" muffin fans were purchased from Radio Shack and wired together with a single plug.

I purchased two pieces of laundry dryer aluminum couplers for the outlet side of the box. These were 4" round tubes with flat mounting plates. You will find these down the venting section at Home Depot. If you fail to find these, do what I do, go back and forth between the plumbing areas and you will find some sort of a substitute material. I also purchased two 25' lengths of expandable aluminum dryer hose for the two columns.

This simple 6-sided box has a removable lid for cleaning, but the dimensions must be taken from your fog unit. Start with the height of the nozzle to obtain the height of the nozzle inlet. Some fog units may need to be elevated to center it in this side of the box. Once this dimension is determined, measure the width of the fog unit and add 12" to it. (If your fog machine is 9" wide the width of your box will be 21".) With a hole saw, cut the nozzle inlet 1/2" larger than your nozzle in the center of that side of the box. Also cut two 4" holes at the same height on the left and right for the muffin fans.

The next step is to cut two holes in the front panel directly in line with the muffin fan holes for the dryer vent couplers. After all these holes have been cut you can assemble the box. The depth of my unit was approximately 12" and came out to 10" high. You want the smoke to have a chance to gather in the box before exiting the other side via the forced air from the fans. I have seen people try to feed smoke through a fan from the back and this is a serious mistake. Oil residue from the smoke fluid will cause a short as it builds in the fan motor, this can cause a fire. Also, never put the fog unit in direct contact with the box itself, the heat at the tip of the nozzle can also start a fire. There is no need to do this anyway, as the draft from the fans will cause the smoke to be sucked into the box.

Once you have assembled the bottom and sides of the box, line it with Heavy Duty aluminum foil. Use a light coating of spray adhesive to hold the foil. Leave the top removable via some screws for easy cleaning. Mount the fans, and dryer vents and complete the wiring to the fans. You can also use this distribution box to supply smoke to two adjoining rooms if needed. Allowing you to trim your budget for fog machines in half!

We hooked up two lengths of 25' aluminum dryer vent hose to the two outlets and ran one to each stone column. These were threaded through the bottom of the columns to enable the smoke to rise and exit out the tops of both. Each column had two small PAR lamps with orange and yellow gels. This is where some sort of flicker generator would come in handy had we had the time and budget. From here it is just a matter of turning on the fog machine, setting it on an automatic cycle, (Ours was set to run for 15sec. every 30sec.) plug in the lights and fans and you have an excellent cold fire effect. The resulting effect was quite impressive, and well worth the added time and money it took to build the effect. Our client was quite pleased, as were the thousands of patrons who saw the effect.

Matt Marich has worked in the film industry for 18 years on such films as Tombstone, The stand, Creepshow II, Body Snatchers, and Bill & Ted's Excellent Adventure. Co-owner of Edge Designs & Theme Deco, Inc. in Phoenix, suppliers of sets, Props and Interactive Displays for Trade Shows, Theme Parks, and Corporate Clients. He can be reached at 623-580-8148, or via email at EdgeDecor@aol.com

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