Test Procedure

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• Air Pressure
• Air Line Filter

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Air Pressure

To determine if the safety container would be able to withstand the pressure if the aerosol can was accidentally discharged or if a leak occurred, the safety container was pressure tested. The vapor pressures of the propellant indicate the pressures that could be present at a given temperature. If the aerosol canister is in an unpressurized vehicle, the maximum additional pressure that the safety container would be subjected to would be about 15 psi.

The end cap of the safety container was drilled and tapped so a Schrader tire valve could be attached (figure 1). The container cap was attached and the container was pressurized to 150 psi (figure 2). The loss of air pressure in the container was recorded over 4 hours. None of the containers leaked when the cap was tightly sealed.

Figure 1—A PVC safety container for bear
repellent spray. A Schrader tire valve has
been attached to the cap.

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Figure 2—The PVC safety container was pressurized to
150 psi and monitored for 4 hours. So long as the container
was properly sealed, the pressure did not drop.

A test was conducted with the aerosol can inside the safety container and the can's nozzle depressed (figure 3). The pressure was recorded, confirming that the pressure in the system approximated the vapor pressure of the propellant at the indicated temperature.

Figure 3—The PVC container was modified so the bear
repellent spray could be discharged inside the container.

Air Line Filter

The effectiveness of the filter system was evaluated without sophisticated equipment. The aerosol can was placed inside the safety container and the lid and valve were sealed. The aerosol can nozzle was depressed, the inside of the safety container was pressurized, and the nozzle was released. The needle valve installed between the Schrader valve and the container was connected to a 10-micron filter. The needle valve was opened and the contents of the safety container were passed through the filter (figure 4). Aerosols typically do not have many particles (less than 14%) smaller than 10 microns. The gases downstream of the filter were smelled to detect the pepper aerosol.

Figure 4—One test used a filter to remove aerosol
particles after the bear repellent spray
was released inside the container.