Opening a can of new tennis balls is usually uneventful, but the unique packaging introduces a potential for injury. The sealed containers hold compressed gas necessary to maintain the balls’ performance. This pressurization creates a hazard upon opening. Understanding the physical forces involved can encourage safer handling of this common sporting equipment.
Understanding the Pressurization
Tennis balls are sold in airtight cans because they are internally pressurized, typically around 12 to 14 pounds per square inch (psi) above atmospheric pressure. The can is sealed with a corresponding pressure to prevent the air from leaking out of the porous rubber core over time.
When the seal is broken by the plastic ring pull, the pressure inside the can is suddenly released, creating the familiar “pop” sound. This release can forcefully propel the lid or small particles upward. Although the plastic lid is designed to contain this pressure, a failure in the seal or an unexpected twist can turn the lid into a projectile.
Specific Injury Risks
The sudden release of the pressurized lid or a sharp edge from the can can lead to two primary categories of injury: ocular trauma and hand lacerations. The most significant danger is to the eyes, especially if the can is held close to the face while breaking the seal. Projectile lids can cause blunt force trauma, resulting in serious conditions like hyphema (bleeding in the anterior chamber of the eye) or corneal abrasions.
The impact from a blunt object can transmit force through the eyeball, potentially leading to a retinal detachment. This is a medical emergency. The thin metal edges of the can, once the lid is partially removed, also pose a significant risk of laceration to the fingers and hands. These sharp edges can cause deep cuts or puncture wounds if the opener’s hand slips due to the sudden pressure release.
Essential Safety Guidelines
To prevent injury, the most straightforward safety guideline is to ensure the can is never pointed toward the face or other people when the seal is broken. Always direct the top of the can away from your body and the faces of anyone nearby. Using two hands to hold the can and the pull-tab provides better stability and control, reducing the chance of an uncontrolled release.
Use a smooth, steady motion when pulling the tab to break the seal, rather than a quick jerk or twist. This gradual motion helps manage the pressure release. If the can is metal, immediately dispose of the sharp, separated lid to eliminate the risk of accidental cuts during ball retrieval.