Backaround of the Prior Art There is a need to have indoor firing ranges available to law enforcement officers. It is an irony that in an era when law enforcement officers are seeing unprecedented challenges to authority, and unprecedented demands on their proficiency with firearms, that many officers are denied access to indoor firing ranges because of lack of funds.

Throughout the United States of America, many existing and otherwise functional indoor ranges have been abandoned because of inadequate ventilation and inadequate funds to provide ventilation systems that would bring the ranges into compliance with indoor air quality standards and exhaust air emission regulations of OSHA, and the recommendations of the National

Institute of Occupational Safety and Health (NIOSH).

Experience has shown that when indoor ranges with state of the art ventilation systems are available to police officers, the officers voluntarily use those facilities frequently to sharpen their firearm skills.

Conversely, when only outdoor ranges are available at some remote locations, officers are less likely to make voluntary visits to the range to improve their skills. The only time officers fire their weapons is at mandatory qualifying sessions. Many man hours are lost when scheduled qualifying sessions are cancelled due to bad weather, and those qualifying sessions which must be held in inclement weather become an unpleasant task which everyone wants to get over with and no one gains anything from.

The absolute need for law enforcement officers to be proficient with their firearms to protect the public, to defend themselves, and to avoid injury to bystanders is unquestioned.

The availability of an indoor range allows agencies to meet the proficiency challenge and leads to improved morale and the respect of'fellow law enforcement departments. Also, those concerned with our environment are beginning to look at the lead berms behind targets of our outdoor ranges as sources of lead contamination to ground water, so they may at some time be prohibited. In the near future, law enforcement agencies and governing bodies may come to realize the

importance of an investment in an indoor range.

Perhaps when that time comes, funds for indoor ranges will be made available from the government.

A report entitled LEAD EXPOSURE AND DESIGN CONSIDERATION FOR INDOOR FIRING RANGES by Thomas L.

Annaiya and Joseph A. Seta, published in December 1975 by the U. S. DEPARTMENT OF HEALTH, EDUCATION, AND WELFARE, Public Health Service, Center for Disease Control, National Institute for Occupational Safety and Health, Division of Technical Services, Cincinnati, Ohio 45202 is incorporated herein by reference, and a copy is enclosed.

Summary of the Invention The present invention provides a method and apparatus comprising an adjustable ventilation system for an indoor firing range room which controls velocity, pressure, and even distribution of air passing from behind a shooter station down range to be exhausted from the room at the down range end. The air passing through the firing range room does not swirl and does not return contaminates to the shooter firing positions where it might be inhaled by a shooter.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic view of a typical floor plan of an indoor firing range; Fig. 2 is an exploded view in perspective of an

airwall module, top plenum chamber, and a movable perforated air balancing plate.

Fig. 3 is a view in top plan of the top plenum chamber.

Fig. 4 is a view in front elevation of the top plenum chamber.

Fig. 5 is a view in vertical section of the top plenum chamber taken along the lines and arrows 5-5 which appear in Fig. 3.

Fig. 6 is a view in perspective of the movable perforated air balancing plate.

Fig. 7 is a view in perspective of an airwall module.

DETAILED DESCRIPTION OF THE DRAWINGS Turning now to the drawings, Fig. 1 shows an indoor firing range room 11 and discloses a fan 13 for supplying intake air from the outdoors 14 to the firing range 11 through a duct 15.

A heater 19 may be connected to the duct 15 for heating the air when necessary or desirable.

A series of airwall modules 21 are connected side- by-side and supply a uniform, horizontal flow of air from behind shooter firing positions 23 to provide a constant breeze, indicated by the arrows 25,26, and 27, for conveying gunsmoke down range and away from the shooter firing positions 23.

Airwall modules 21 are prefabricated from sheet

steel into enclosed box housings 28 with an airwall face 29 made of a perforated aluminum sheet with perforations or holes 31 through which the air is forced.

If desired, the airwall module 21 may include a solid, high strength, heavy gauge ultraclear plastic sheet rear wall 33 and the same type of clear sheet with perforations for a front wall 35 so that the firing positions and shooters may be viewed from the rear of the room by an instructor with no loss of air distribution.

Also, if desired, an air door 37 may be provided comprising a steel entry door connected through the airwall 21 where access to the airwall 21 is required.

The airdoor 37 contains perforated front and rear panels so that the airdoor causes no interruption of airflow.

An exhaust air fan 39 is connected to the firing range room 11 by an air duct 41 for exhausting the air from the firing range room 11 to the outdoors 14.

A bullet trap 43 is positioned down range from the firing stations 23 for catching the lead bullets.

In operation, the method for providing proper ventilation for the indoor firing range 11 which has an air intake end 17 and a down range exhaust end 47 comprises the steps of supplying intake air to the intake end 17 of the room 11 from the outdoors 14, receiving the intake air in top plenum chamber 49 and

pressurizing the intake air in the plenum chamber 49, passing the intake air from the plenum chamber 49 into an airwall housing 51, discharging the air horizontally from the airwall housing 51 through holes 31 into the room 11 so that the air flows down range, providing a uniform horizontal flow of air from behind the shooter firing stations 23 in the firing range room 11 and providing a constant breeze for conveying gunsmoke down range and away from the shooter firing stations 23, exhausting the air from the down range end 47 of the room 11, and adjustably controlling the velocity, pressure and even distribution of the air passing from the plenum chamber 49 into the airwall housing 51.

Such adjustably controlling is accomplished by adjusting the position of a movable perforated plate 53, with airholes 55, relative to the position of a fixed perforated plate 57 with airholes 59 positioned between the top plenum chamber 49 and the top of the airwall modules 21 so as to vary the size of the air passages through the holes 59 in the fixed perforated plate 57.

The method of adjusting the air flow in the indoor firing range ventilation system comprises the steps of providing a fixed perforated plate 57 between top plenum chamber 49 and the top of airwall housing 51 with the fixed plate 57 having air holes 59 forming passageways for air, providing a movable perforated plate 53 on top of said fixed perforated plate 57 with

the movable plate 53 having air holes 55 forming passageways for air, testing the air flowing from the airwall 21 through the firing range, and adjusting the position of the movable plate 53 in response to the testing results to vary the size of the air passageways through the holes 59 in the fixed plate 57.

The pressure in the exhaust air duct 41 is lower than the pressure in the entrance air duct 15. This arrangement keeps the contaminates and pollutants going down range so that the officers doing the firing do not inhale lead contaminated air.

The invention provides smoother air flow and simple, on-site balancing of the air flow so that it flows straight down range with no swirling. Exterior air is taken into the firing range room 11 and is pressurized in the top plenum chamber 49 by the fan 13 and is distributed through the front panel 52 of the airwall housing 51.

The fan 13 is adjustable to provide a desired cubic feet per minute of air into the shooting stations.

As shown in Figs. 4 and 5, the top plenum chamber 49 is provided with a gasket 61 which is held in place by a galvanized metal strip 63 and bolts and nuts 65.

Studs 67 project from the rear face of plenum chamber 49 and when the movable plate 53 is moved into its desired position, nuts 68 may be turned to abut flange 54 of movable perforated plate 53 and hold it in

the desired position.

The indoor firing range system of the invention equalizes the air flow behind the distributing wall 52 of the airwall housing 51 so that the air comes out of wall 52 flowing more uniformly. The invention also changes the incoming turbulent air to an even flow with increased static pressure in the top plenum chamber 49 as compared to the pressure in the airwall module 21.

Initially, the air flow is greater than that required for the system, and by partially closing the openings or air holes 59 in the fixed perforated plate 27 by moving the movable perforated plate 53, the air flow is adjusted to the desired air flow.

The fans, duct work and other system components are designed to deliver the proper volume of air to obtain 75 fpm velocity at the firing station line 23.

The system may heat or cool the incoming air.

Heating is obtained through gas, hot water, steam or electric power, whatever is preferred. Cooling is obtained through adding chilled water or an electric refrigeration system.

The entire rear wall of the range is covered with airwall modules 21, bolted together side by side, forming a continuous perforated plenum. This system delivers the air evenly along the entire area of the firing line.

It is recommended that the airwall be placed 15 feet behind the shooter. However, the system also

works properly at closer distances such as 8 to 10 feet behind the shooter.

The system is designed so that the supply air fan 13 delivers the proper volume (CFM) of air to obtain 75 fpm at the firing line 23. Exhaust air fan 39 is designed for 10% more air volume in order to maintain a negative pressure in the range room 11 and keep contaminates from migrating to other parts of the facility.

The system is designed to place the exhaust grills and duct 41 along the entire down range exhaust end 47 at the apex of the bullet trap 43.

The system is designed with a minimum down range air velocity of 35 fpm, and the invention is generally better than the minimum, and averages between 50 to 60 fpm.

The system is a once through, purged system so 100% of the air is exhausted down range at the bullet trap 43. Exhausting 100% of the air at the bullet trap 43 also ensures that the minimum conveying velocity of 35 fpm is maintained down range.

The system has a specially designed electric control system so that the supply fan 13 and exhaust fan 39 are interlocked. When the system is energized, the exhaust fan 39 comes on, the supply fan damper starts to open and when it is fully opened an end switch is made and the supply fan 13 comes on. This sequence ensures negative pressure in the range.

The system is a once through, purged system. None of the range air is ever recirculated back to the range with the chance that unfiltered air could be breathed by the shooter.