Several studies have documented the effectiveness of bear spray in protecting users from aggressive bears. Bear spray failures, however, have also been reported along with speculation regarding the influences of temperature, wind, repeated canister use, and canister age on spray efficacy. We designed lab and field experiments to document the influence that temperature, wind, repeated discharges from the same canister, and canister age have on bear spray performance. To determine the influence of temperature on spray performance, we recorded canister head pressures at temperatures ranging from −23°C to 25°C and found a strong, positive linear relationship. Even at the lowest temperature tested (−23°C), bear spray had a range >4 m, though the plume was narrow and the spray was not well aerosolized. As canister temperature increased, head pressure, plume distance, and dispersion increased. We used computational fluid dynamics modeling and simulated the effect that headwinds, crosswinds, and tailwinds of varying speeds had on spray performance. Even under high headwind and crosswind scenarios (>10 m/sec), sprays reached targets that were approximately 2 m directly in front of the user. Crosswinds affected spray plume distance similar to headwinds, but the effect was not as pronounced. Tailwinds improved spray performance with respect to speed and distance. By weighing unused canisters ≤18 years old, brands tested lost weight ranging from 0.65 g/year to 1.92 g/year, presumably because of propellant that escaped canister seals. We also documented that bear spray head pressure declines in a logarithmic, not linear, fashion; over half of a new (7‐sec spray time) canister's pressure was lost in the first 1 second of spray. We recommend not test‐firing cans, keeping cans warm when in the cold, and retiring them when ≥4 years of age. Our results provide no compelling reason to not carry bear spray in all areas where bears occur, even if it is windy or cold. © 2020 The Wildlife Society.

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影响熊喷雾性能的因素研究

多项研究已证明熊喷剂在保护使用者免受侵略性熊侵害方面的有效性。但是，也有报道称熊熊喷雾失败，并且有关于温度，风，重复使用碳罐以及碳罐年龄对喷雾功效的影响的推测。我们设计了实验室和野外实验，以记录温度，风，同一罐的反复排放以及罐龄对熊喷雾性能的影响。为了确定温度对喷雾性能的影响，我们记录了在-23°C至25°C范围内的温度下的罐头压力，并发现了强烈的正线性关系。即使在测试的最低温度（−23°C）下，熊喷雾的范围也> 4 m，尽管羽流较窄且喷雾未得到很好的雾化。随着容器温度的升高，头压 羽流距离，且色散增加。我们使用了计算流体动力学模型，并模拟了不同速度的迎风，侧风和顺风对喷雾性能的影响。即使在逆风和侧风情况下（> 10 m / sec），喷雾也可以直接在用户面前达到约2 m的目标。侧风对喷雾羽流距离的影响与逆风相似，但效果并不明显。尾风在速度和距离方面改善了喷雾性能。通过称重≤18年的未使用的碳罐，品牌测试的重量减轻了0.65克/年至1.92克/年，这大概是因为推进剂逃脱了碳罐密封。我们还记录了熊的喷头压力以对数而不是线性的方式下降。超过一半的新罐（喷雾时间为7秒）” 在喷涂的前1秒内压力下降。我们建议不要对罐进行试烧，在寒冷时将罐保持温暖，并在≥4岁时退役。我们的结果没有令人信服的理由，即使在刮风的地方或寒冷的地方，在出现熊的所有区域都不要携带熊喷雾。©2020野生动物协会。