Public Works Department Sewer Maintenance Division truck used for explosive gas survey, ca.1938

Photograph of a Public Works Department Sewer Maintenance Division truck used for explosive gas survey, ca.1938. At center, a man in a blazer jacket can be seen standing inside a small, striped van. In the background, a brick building with a line of square windows can be seen. An automobiles can be seen at left. Additional information: The photograph features a "route truck" used by the Public Works Department Sewer Maintenance Division for testing and reporting explosive gas conditions in sewers. The truck carried a two-person crew consisting of a driver and a tester. The truck also carried a combustible gas testing device powered by a 6 volt battery and actuated by a vacuum from the truck engine. The device could detect gasoline vapor, natural gas and combustibility. The crew could test from 300 to 500 manholes daily. The device used a long copper tube (probe) that was inserted through the pick hole of a manhole cover to "sniff" for explosive gases. Tests were made by driving up to a manhole and simply inserting the probe to draw a sample of the manhole atmosphere. If explosive conditions were detected, they were immediately reported for remediation. The man in the blazer standing in the van appears to be Mr. Alvin Appel, an employee of the Sewer Maintenance Division.

约1938年，一张用于爆炸性气体检测作业的公共工程部下水道维护部门作业卡车的照片。画面中央，一名身着西装外套的男子站在带有条纹的小型厢式作业车厢内。背景中可见一栋带有一排方形窗户的砖砌建筑，画面左侧可见一辆汽车。

补充说明：本照片展示的是公共工程部下水道维护部门用于检测并上报下水道内爆炸性气体状况的「线路作业卡车」（route truck）。该作业卡车搭载由一名驾驶员与一名检测员组成的双人作业班组。车辆还搭载了一套可燃气体检测装置，该装置由6伏特电池供电，并借助卡车发动机产生的真空驱动，可检测汽油蒸气、天然气以及可燃浓度。该班组每日可完成300至500个检查井（manhole）的检测工作。该装置配备一根长铜管（探头），可通过检查井盖板的撬孔插入以「嗅探」爆炸性气体。检测流程为：驾车抵达检查井位置后，仅需插入探头即可抽取检查井内的气体样本。若检测到爆炸性气体浓度超标，将立即上报以开展整改作业。站在厢式车厢内身着西装外套的男子疑似为阿尔文·阿佩尔（Alvin Appel）先生，系下水道维护部门的雇员。