实验室化学防护罩中的危险控制基于以下原则:通过防护罩表面区域吸入的空气足以克服开口处或开口附近的许多挑战。需要克服的挑战包括但不限于发动机罩附近的空气速度、研究人员的移动、走过发动机罩的人、发动机罩内设备的位置、窗扇开口的大小以及入口条件的形状和配置。为了克服这些挑战，必须保持足够的表面速度。 系统设计师、设施安全官员和研究人员应考虑这些问题和其他问题，确定给定发动机罩的正确表面速度。本研究在有人使用的防护罩上以每分钟100英尺（fpm）的表面速度测试安全壳，并在无人使用时以每分钟60英尺（fpm）的降低速度测试相同的防护罩。使用三个不同尺寸的实验室化学防护罩，带有几个窗扇位置。测试结果表明，在测试实验室的理想条件下，根据SI/ASHRAE 110中规定的示踪气体测试，60 fpm时未占用的发动机罩（不带人体模型）所含气体与100 fpm时占用的发动机罩（带人体模型）所含气体相当，甚至更好- 1995，实验室通风柜性能测试方法（ASHRAE 1995）。需要进行进一步测试，以确定在实际使用条件下，这种关系是否相同，即发动机罩凌乱且存在交叉气流。单位:I-PCITION:研讨会，ASHRAE交易，第105卷，pt。1.

Containment of hazards in a laboratory chemical hood is based on the principle that air drawn through the face area of the hood is sufficient to overcome the many challenges at or near the opening. Challenges to overcome include, but are not limited to, air velocities near the hood, movement of the researcher, people walking past the hood, location of equipment inside the hood, size of the sash opening, and the shape and configuration of entrance conditions. To overcome these challenges, a sufficient face velocity must be maintained. Determining that proper face velocity for a given hood should be resolved by the system designer, facility safety officer, and researcher with these and other issues in mind.This research tests for containment at 100 feet per minute (fpm) face velocity on occupied hoods and tests the same hoods for containment at the reduced velocity of 60 fpm when unoccupied. Three laboratory chemical hoods of different sizes with several sash positions are used. The test results show that under ideal conditions in a test laboratory, an unoccupied hood (without a manikin) at 60 fpm contains as good as, if not better than, an occupied hood (with a manikin) at 100 fpm, as measured by the tracer gas tests specified inANSI/ASHRAE 110-1995, Method of Testing Performance of Laboratory Fume Hoods (ASHRAE 1995). Further testing is needed to determine if this relationship is the same under conditions of actual use, i.e., cluttered hoods and presence of cross-drafts.Units: I-P