Carey's Range Ventilation

Carey's Heating & Air Conditioning, Inc. has designed and built over 120 small arms range ventilation systems since 1995. The majority of these ranges have been tested by an independent industrial hygienist. They have all tested below the OSHA (Occupational Safety and Heath Administration) allowable limits for lead exposure. They in fact have come back with “Less than detectable” readings. It is important to install a proper ventilation system for an indoor range regardless of the type of ammunition that is being used. Although there is no lead in some rounds, the lead has been replaced by other heavy metals such as copper. These are also regulated by OSHA.

There are three main purposes for properly ventilating a small arms range:

The primary purpose for the ventilation of an indoor firing range is to remove contaminates created during the firing of a weapon from the respiratory zone of the occupants. Exploding primers containing lead styphnate and friction from the lead slug against the gun barrel create airborne lead. There is also carbon monoxide as well as other contaminates created during the firing of a weapon.
The second and equally important reason for the properly designed and installed ventilation and control system is to keep the range at a negative pressure to the surrounding base building space. Contaminates created on a small arms range need to be contained in the range space. This will prevent the ingestion of contaminates as well as keeping the surfaces free of contaminates in non-range spaces of the base building.
The final purpose is to remove the smoke from the range for properly seeing the targets.

NIOSH (National Institute of Occupational Safety and Heath), a division of CDC (The Center for Disease Control (and Prevention)) published a report in December of 1975 that detailed suggested designs for small arms range ventilation based on their study. This is, to date, the best standard for the airflow design. These design parameters have been the basis of design for all of the ranges that we have designed. This has also been the basis of design for the United States Navy standards as published in the Unified Force Criteria (UFC 4-160-01), and the United States Air Force Engineering Technical Letter (ETL 06-11) and the GSA Region 5 Design criteria.

The suggested airflow for a small arms range is an average of 75 feet per minute at the firing line. This airflow must be even and have minimal turbulence. There have been two general approaches to the distribution of the air that have proven successful. The first is a plenum wall. Although this can work and some have successfully tested to provide laminar flow, the plenum wall has also been prone to problems. The main problem is when the access door to the range and the window from the Range Safety Office have been installed they tend to create turbulent areas. There have also been problems where the range officer standing in one position has caused a lane to fail the exposure test. The second method that has proven successful is the Radial Diffuser. These are custom built and tested to provide proper airflow at the firing line. It is critical to only use proven products that have been tested to achieve the laminar or even airflow at the firing line.

The negative pressure in the range is very important. Providing laminar airflow at the firing line will protect the shooters respiratory zone, but it will not keep contaminates created in the range from entering the base building area. Providing a negative pressure in the range is accomplished by designing more exhaust than supply air. The industry standard for this design is 10% greater exhaust than supply. This amount varies based on the building construction. The tighter the range area of the building is constructed, the less differential is necessary to maintain the proper pressure differential. The industry standard is a negative .04 to .06” water column negative pressure to the base building area. We have seen many ranges that were designed with this differential, but the exhaust is filtered and there was no method of modulation for the exhaust based on filter loading. This caused the range to go positive within a week of a filter change. It is very important to oversize the exhaust fan and modulate the fan with a Variable Frequency Drive or inlet vein vortex damper. The most critical component to keeping the range negative is a control system that can start up, stop and maintain the range at a negative at all times. The control system must also monitor the range conditions and alarm and shut down if unsafe conditions are present.

It is important to filter the airflow even if 100% of the air is exhausted. Although the emissions of the range is below the federal EPA (Environmental Protection Agency) levels for industrial exhaust, the lead dust can collect at the ground or roof and exceed the surface levels acceptable to the EPA. We suggest that the final level of filtration is a HEPA (High Efficiency Particulate Arresting) filter with that will filter 99.97% of the particles that are 0.3 microns or larger.