BASIC PRINCIPLES IN OCCUPATIONAL HYGIENE 职业卫生基本原则 Day 2 第2天

10 – VENTILATION 10-通风

GENERAL VENTILATION 全面通风

Local exhaust ventilation (LEV) systems Photo showing typical components in a real LEV system LEV系统组成实例 Source: Adrian Hirst 资料来源：Adrian Hirst

General Features of an LEV System 常见LEV系统组成 风扇 排气口 管道 空气净化器 外罩 Source: Adrian Hirst 资料来源：Adrian Hirst

General Considerations 一般注意事项 来源，速度方向 有效控制 D LEV 外罩 类型、大小、气流 B工序要求 封闭罩数量，LEV最有效使用的重新设计程序 C 对操作人员的要求 确保外罩与作业方式协调 Source: HSE 信息来源： HSE

Inlets/Hoods 进气口 /外罩

Local exhaust ventilation hoods: 局部排气通风罩 Capture mobile 侧向吸气罩 局部罩 倒风吸气罩 吸尘罩 隔尘帘 There are a large range of different types and designs of LEV hood and there appears to be no common design principles. LEV外罩类型多样，设计多样，几乎没有相同设计原理。 The new HSE guidance (HSG 258) states that there are only three types of LEV hood.全新HSE指南（HSG258）中规定，仅有三种类型的LEV外罩。 集石盒 溢回橡胶密封 柜形吸气罩 伞形吸气罩 密封罩 Source: HSE 信息来源： HSE

The three basic types of LEV hood Enclosing (Contain and separate) 封闭外罩 （容纳式，隔离式） Receiving (Receive, contain & empty) 受体罩（接受式，包含式，和清空） Capturing (Capture) 采集罩（采集式） Enclosures – process takes place inside the hood. The hood needs to contain the airborne contaminant and keep it separate from the worker 封闭罩–工序在外罩内部进行。外罩容纳空气污染物，将其与员工分离。 Receptor – process takes place outside of the hood, but the process generates directional air movement towards the hood. The hood needs to receive the contaminated laden air and to ensure it works effectively it needs to empty at lease as quick as it is being filled. 受体罩——工序在外罩外围进行，但会产生相对于外罩的定向空气流动。外罩需要接受污染的空气，为保持其确保其有效运作，一旦充满，应立即清空。 Capturing – process takes place outside the hood. The hood has to generate sufficient air movement towards the hood at the far side of the source. Effectively, the hood has to reach out and capture the contaminant laden air. 采集罩——工序在外罩外围进行。相对于污染源远端外罩，产生足够的空气流动。实际上，外罩需要接触并采集空气。 Most LEV hoods fall into one of the above categories, but sometimes hoods do operate in ‘mixed mode’ 大多数LEV外罩均不属于上述三种类型，有时外罩操作模式是“混合型”。 Source: HSE 信息来源： HSE

LEV hood classification expanded Enclosures 封闭罩 进气 过滤器 Full 全面型 Partial, large 局部型，大型 Partial, small 局部型、小型 Room 室内型 出气 过滤器 Receiving 受体罩 Hemeon refers to three different types of hood; exterior (which is equivalent to capturing), enclosing and Canopy or receiving hood Hemeon系指三种不同类型的外罩;外部式（相当于采集式）；封闭式和伞形罩或受体罩 Enclosures – Can be subdivide - full, partial (large), partial (small), room 封闭外罩——又可以细分——全面封闭式，局部封闭式（大型）、局部封闭式（小型）、室内式 Receiving – Process moves in one direction. classic receiving hood is the canopy hood above a hot process 受体罩——单向工艺处理。传统受体罩是伞形罩，位于热流上方。 In practice the guidance will use the classification to outline key design factors for each type of hood and common errors but also will refer to and use the more familiar terms where appropriate e.g. enclosure, partial enclosure and canopy hood 在实践过程中，指南将使用分类法列出各类型外罩的设计要点和常见错误点，还会引述和使用常用术语，例如封闭式外罩、局部式外罩和伞形罩。 Hot 热流 Capturing 采集罩 Source: HSE 资料来源：HSE

LEV system design, the most critical element is the hood Main reasons why systems fail to protect: 系统无法提供保护的主要原因： Incorrect type of hood is chosen (and could never provide sufficient protection) 所选外罩类型不当（根本不能提供足够的保护） The airborne contaminant isn’t contained or captured. 不能容纳或采集气载污染物 LEV hood design doesn’t match the process and source(s) LEV外罩与工艺和污染源不符 Insufficient airflow (various reasons). 气流不足（各种原因）。 Most LEV systems fail to control exposure because the airborne contaminant never enters or doesn’t stay in the hood 大多数LEV系统无法控制风险，因为气载污染物污染进入或留在外罩内部。 Various reasons include: poor maintenance leading to hood damage, duct and/or air-cleaner blockage, holes in ductwork, system goes out-of-balance (various reasons including opening and closing of dampers), fan performance degrades (e.g. damage to blades or housing, drive-belt breakage or slippage) 各种原因包括：保养不善，导致外罩受损；管道和/或空气滤清器堵塞；管道出现孔洞；系统失衡（包括风门启闭）、风机性能减退（例如，叶片或外罩有损、驱动皮带断裂或滑脱） Insufficient airflow – degrades with time. Often a system will make the same noise as the day it was installed, but the flow rate could be dramatically lower. 气流不足——随着时间的推移而下降。通常情况下，系统的噪音自安装之日起就不会发生变化，但流率会随着时间而出现大幅降低。 Source: HSE 资料来源：HSE

(adapted from Hemeon’s Plant and Process Ventilation) Capturing Hoods 采集罩 Process takes place outside hood, hood-induced airflow has to “capture” contaminant-laden air 工艺在外罩外围实施，外罩促发式气流应采集污染空气 Capture hoods often ‘shoe horned’ into a process as an afterthought. Therefore, placed where it can be fitted rather that where it should be placed. 采集罩通常是工序的“候补措施”。因此，应按需放置，不应按规定放置。 Side-draught captor hood 侧向气流式采集罩 (adapted from Hemeon’s Plant and Process Ventilation) （取自Hemeon的厂房和工艺通风） Source: HSE 资料来源：HSE

(adapted from Hemeon’s Plant and Process Ventilation) Capturing Hoods 采集罩 The process, source and contaminant cloud are outside the hood 工序操作、污染源和污染物云均在外罩外围。 Hood has to generate sufficient airflow at and around the source to ‘capture’ and draw in the contaminant-laden air 外罩需要在污染源附近和周围产生足够的气流，以“采集”并吸入污染气体 All capture hoods work on the same principles – regardless of size 所有采集罩的工作原理相同——与其大小无关 (adapted from Hemeon’s Plant and Process Ventilation) （取自Hemeon的厂房和工艺通风） Source: HSE 资料来源：HSE

Capturing Hoods – interrelated properties 采集罩——相关联特性 Capture velocity, distance and zone (new(ish)) 采集速度、距离和区域（全新） Process induced air movement and draughts 空气流动和通风方法 Airflow, velocity contours and flanges 气流、等流速线和凸缘 Capture ‘bubbles’ (new) 采集“气孔 ”（新增） Capture curve (new) 采集曲线（新增） Capture zone and Working Zone (new). 采集区和工作区（新增） Some of the above are new concepts or new ways of expressing hood properties. 上述某些内容为全新的外罩特性新概念或新方法 Source: HSE 资料来源：HSE

Capture of vapour-laden air: evaporation 采集蒸汽式空气——蒸发 Air velocity required at this point to “capture” vapour-laden air ~0.5 metres per second (m/s) 采集蒸汽式空气的空气流速~0.5米每秒（米/秒）。 Quiet source – e.g. evaporation of solvent. Relatively low capture velocity required 污染源单一——例如，溶剂蒸汽。采集速度相对较低 Source: HSE 资料来源

Capture of vapour-laden air: drum filling 蒸汽空气采集：桶装型 Air velocity required at this point to “capture” vapour-laden air ~2.5 metres per second (m/s) 采集蒸汽式空气的空气流速~2.5米每秒（米/秒）。 More energetic process – hence larger capture velocity required 动态化程度较高的工序——所需采集速率偏高。 Source: HSE 资料来源：HSE

Receptor Hoods 受体罩 Source: HSE 资料来源：HSE

Enclosing Hood 封闭罩 Source: HSE 资料来源：HSE

Types of LEV used for various processes 各工序用LEV类型 Industrial process 工序 Nature of hazardous substance 危险物质性质 Types of LEV LEV 类型 Welding 焊接 Welding fume: fine particulate with some natural buoyancy 焊接烟尘：有天然浮力的细颗粒 Capture hood positioned close to the welding activity; or Tip extraction fitted to the end of the welding gun 靠近焊接操作的采集罩；或安装在焊枪末端的焊料提取 Paint spraying 喷漆 Mist and solvent vapours released in controlled direction with velocity 排放方向和速度受控的漆雾和溶剂 Walk in paint spray booth 喷漆房内走动 Down flow booth 降流外罩 Polishing 抛光 Metal and polishing dust released in controlled direction with high velocity排放方向和速度受控的金属和抛光粉尘 Receptor hood and enclosure around the polishing wheel 抛光轮周围的受体外罩和封闭罩 Shot blasting 抛丸 Steel shot and metal dust from components released at high velocity in variable direction 以高速变向释放的组件中的钢丸和金属粉尘 Fully enclosed glove box type cabinet with airflow managed to compensate for compressed air input and shot recycling system 全封闭的手套式操作箱（气流受控，可对进气和钢丸循环系统进行补偿） Hand held orbital Sander手持轨道 、磨沙机 Wood dust released in variable directions 变向释放的木屑 Extraction integrated into the sander disc 从砂光机中的提取 Paint curing Ovens 涂料固化 烘炉、 Hot air and curing vapours with strong thermal buoyancy 热浮力强的热空气和固化蒸气 Extract/vent from top of oven combined with a receptor hood over the doorway 从在门口配置有受体外罩的烘炉顶层的提取/排出 Laboratory analysis 实验室分析 Acid and solvent vapours released with low velocity and little direction 低速和小角度排放的酸与溶剂蒸气 Partial enclosure and extraction within a fume cupboard 部分封闭，从通风橱内提取 Source: HSE 资料来源：HSE

Capture Zone / Capture Bubble 采集区/采集气孔

Capture bubble 采集气孔 Movable capturing hood – capture ‘bubble’ 移动式采集外罩——采集气孔 Capture bubble 采集气孔 Can think of the capture zone as a bubble.可以将采集区视为采集气孔 Source: HSE 资料来源：HSE

Capture ‘bubble’ varies in size 采集气孔大小不同 Capture bubble will vary in size depending upon air movement in the room – degree of draughts in the room.采集气孔大小不同，大小取决于室内空气流动——室内气流强弱。 Source: HSE 资料来源：HSE

Capturing hood capture ‘bubble’ 采集罩的采集气孔 Demonstration of the change in size of a capture bubble. 采集气孔大小变化示例 Worker soldering in front of a capturing hood – okay at one position, but as she moves away capture falls – small ‘capture bubble’ 工人在采集外罩正前方焊接——仅限固定位置，一旦操作人员移动，采集功能失效——小型采集气孔 Source: HSE 资料来源：HSE

Capture zone must encompass working zone 采集区应在工作区周围 Shows capture zone and working zone. Capture zone must encompass the working zone. if it does not the hood is not effective. Hood has failed to control exposure. 采集区和工作区图片。采集区必须在工作区周围。如未能置于周围，该外罩无效。无法控制风险。 Source: HSE 资料来源：HSE

Ductwork 管道 Ductwork carries the extracted air and the contaminant from the inlet to the air cleaning device. 管道系统将从进气口提取的空气和污染物排放到空气净化装置中。 Velocity Important 速度是关键 Should be sufficiently strong 管道应有足够的强度 Well supported and capable of withstanding normal wear and tear 支撑良好、能够承受正常的磨损 The number of changes of directions should be kept to a minimum 应确保变向次数最少 Should be made smoothly 应确保变向顺畅 Access to ducting may be required. 应配置管道检修口

Duct Velocity 管道流速 Type of contaminant 污染物类型 Duct velocity (m sec-1) Gases (non‑condensing) 气体（非冷凝） No minimum limit 无最低限制 Vapours, smoke, fume 蒸气、烟雾、烟气 10 Light/medium density dust (e.g. sawdust, plastic dust) 轻/中密度粉尘（如木屑，塑料粉尘） 15 Average industrial dusts (e.g. grinding dust, wood shavings, asbestos, silica) 工业粉尘平均速度（例如磨削尘、刨花、石棉，硅石） 20 Heavy dusts, (e.g. lead, metal turnings and dusts which are damp or that tend to agglomerate) 重金属粉尘（如铅、金属屑和潮湿易结块的粉尘） 25 Source: HSE 资料来源：HSE

Air Cleaners – Filters 空气滤清器——过滤器 Source: Adrian Hirst 资料来源：Adrian Hirst

Air Cleaners – Cyclones 空气滤清器——湿式旋风除尘器 Source: Adrian Hirst 资料来源：Adrian Hirst

Air Cleaners - Wet Cyclone & Induct Spray 空气滤清器——湿式旋风除尘器和喷雾引射器 Source: Adrian Hirst 资料来源：Adrian Hirst

Air Movers – Fans 通风器 –风扇 图1：轴流风机 外罩 风扇轮 出气口 气流 进气 Axial Centrifugal 离心式 轴流式 Source: US EPA 资料来源：US EPA

Discharge to Atmosphere 排入大气 不推荐采用“中国帽”式 不推荐 Source: HSE 资料来源：HSE

Maintenance, Examination and Testing of Ventilation Systems 通风系统的维护、检查和测试 In order to function correctly it must be in good working order. 为了确保正常工作，LEV必须保持良好的运转状态。 Legal requirements 法律要求 Regular Maintenance 定期维护 Thorough Examination and Testing. 全方位检查和测试