Personal Protective Clothing

Protective clothing is an important aspect of safety, and the guidelines presented here should be followed when working at industrial facilities.

• Hard hat – All persons entering a confined space are required to wear a hard hat. A full‐strength hard hat with a brim and chin strap provides protection from head injuries. Hard hats may also prevent injury during process area walk‐throughs.
• Coveralls – A person’s skin should be covered as much as possible to prevent scrapes and cuts and to avoid skin contact with hazardous substances.
• Gloves – Hand protection is necessary when working with and/or operating machines and handling liquid, gas, and solid materials. In addition to preventing absorption of hazardous chemicals (e.g. solvents, biological hazards, etc.) and/or heat through the skin, gloves will protect the hands from cuts, scratches, or heat stress.
• Shoes – Rubber‐soled, non‐skid, protective‐toed shoes (e.g. steel, composite) and boots must always be worn in or around a confined space, in process areas, chemical storage areas, etc. Safety shoes are designed to protect against impact and/or hazardous chemicals.
• Ear plugs – Ear plugs should be worn when working in areas with high noise levels (e.g. general manufacturing areas). This equipment will protect employees and personnel from the cumulative effects of loud noises in the work place.
• Safety goggles – Safety goggles are necessary during working in manufacturing industries to prevent eye contact with hazardous substances. Contact lenses are often prohibited around some industrial processes such as plating operations. If a hazardous substance comes into contact with a person’s eye through splashing or exposure to mists or vapors, that substance may become trapped behind the lens where it would be difficult to flush out and could cause severe eye damage.
• Safety vests – Safety vests are necessary warning devices in industrial workplace areas with vehicle traffic.

Communication Devices

Two‐way radios and cell phones are effective ways to maintain contact with a main safety office. For hazardous sites, a sampling team should make contact upon arrival and departure from each sampling location. Industrial off‐sites are often located in unpopulated areas; therefore, it is important that the radio or cell phones be kept in working order in the event it is necessary to call for help. If an accident should occur, the rescuer must call for help before any assistance is given to the victim.

Air Monitoring Devices

Before entering in a confined space, tests should be done for (i) explosive gases, (ii) the presence of toxic gases, and (iii) oxygen deficiency. The most effective method for detecting these conditions is with an atmospheric monitor. The gas detectors discussed in the following are the most commonly used for atmospheric monitoring.

• Single purpose detector – Designed to detect specific gases, such as carbon monoxide, methane, or hydrogen sulfide. These gases are commonly present in various systems and confined spaces. Single detection units or tubes are available for measuring gases that are less common.
• Dual purpose detector – Capable of detecting lack of oxygen and explosive conditions in an area.
• Combination detector – Capable of detecting a lack of oxygen, explosivity, and the presence of toxic gases. This type of meter provides maximum protection by detecting the presence of all three hazards. Hydrogen sulfide and carbon monoxide are the gases usually measured because they occur most frequently in a confined area or in an anoxic system.

The atmosphere in a confined space can change suddenly; therefore, a detector that continuously monitors the atmosphere is recommended. In addition, detectors should be equipped with an audible and visual alarm that is activated in response to specific hazardous conditions or a low battery, thus eliminating the need for taking the time to read a dial or gauge.

It is important to remember that using an atmospheric tester does not ensure safe conditions. Gas detectors are only one source of information pertaining to a potentially hazardous situation. Most gas detectors are designed to test for common gases such as hydrogen sulfide and are not effective for detecting less common substances such as trichloroethylene vapors. There are test kits available for detecting the less common gases. The kits consist of a bellows‐type pump and glass tubes containing an indicator chemical which are sealed at the ends until they are used. The indicator chemical in the detector tube is specific to a particular contaminant or group of gases. A predetermined volume of air is drawn through the tube and the contaminant reacts with the indicator chemical, producing a color change that can be compared to a color calibrated chart to determine an approximate concentration.

When measuring explosivity, gas meters measure the percentage of the lower‐explosive limit (LEL) of a calibration gas, which is usually methane. Gases are combustible throughout a range of air mixtures.

The meters do not differentiate between gases, but they only indicate explosivity relative to the calibration gas. The range begins with the LEL, which is the lowest concentration of a combustible gas or vapor in air that is necessary to support combustion. The explosive range extends upward to the upper explosive limit (UEL) which is the maximum concentration that will support combustion. If the concentration of gas is below the LEL, there is insufficient fuel to support ignition. Alternatively, if the concentration is above the UEL, there is insufficient oxygen to support combustion. These limitations in the atmospheric monitoring equipment emphasize the need for constant ventilation and awareness of potential hazards.

5.12.1.1 Estimate of Dilution Air

When volatile substances are emitted in working spaces such as a laboratory, fresh air is ventilated into the working space to maintain average concentration of the volatile matter below TLV–TWA. The quantity of such dilution air in CFM (cubic feet/minute) may be estimated by

(5.11)

where

• W = mass of volatile matter evaporated/time (lb/min)
• M = molecular mass of the volatile matter
• TLV = threshold limit value of the volatile substance (ppm)
• K = nonideal mixing factor = 0.1 to 0.5 for most situations