Clean areas

Figure 2.23 Shallow pitting in crevice areas on a 304 stainless steel coupon exposed to a misting atmosphere. Note the relatively clean areas where the washer teeth contacted the coupon surface. (Magnification 7.5x.)...

Some large-particle penetration 24 hr or longer sample required in clean areas for mass measurement automated version relatively untested in remote locations... 

Poorly cleaned surfaces may not image well. While ordinary dry dust will be brushed aside by the tip and will not affect the image, oily or partially anchored dirt will deflect the SFM tip or interfere with the conductivity in STM. The result is usually a line smeared in the scan direction, exactly as one would expect if the tip began scanning something which moved as it was scanned. If the sample cannot be cleaned, the best procedure is to search for a clean area. 

Safety hazards are treated in the same manner. For example, workers who work in trenches in clean areas of the site would be covered by the OSHA Excavation and Trenching Standard, Subpart P, 29 CFR 1926. Workers who work in trenches in contaminated areas would fall under both Subpart P and HAZWOPER. Workers who do not work in trenches fall under HAZWOPER only when working in contaminated areas and would not be covered by either standard when working solely in clean areas, provided they are not exposed to safety hazards resulting from hazardous waste operations. 

Flazardous waste sites are divided into as many or as few zones as necessary to protect worker health and safety. Work zones are established to prevent the spread of hazardous substances from contaminated to clean areas. Radiological work zones should be considered compatible with hazardous waste work zones, differing only in terminology. Diagrams, sketches, and maps should be used as often as necessary and constantly updated and communicated so that workers can be sure that they are appropriately protected [3]. 

Procedures to prevent contamination of clean areas (appropriate barriers, plastic sheeting, etc.)... 

Site H was the only site at which the contractor had implemented comprehensive and effective site control elements. The Site H contractor had established site work zones, a buddy system, and site communication procedures consistent with 1910.120(d). This contractor had also established exclusion zones and contamination reduction zones to control migration of site contaminants to clean areas of the site when work within these areas introduced the potential for exposure to hazardous contaminants. The audit team supported this contractor s use of flexible and temporary work zone boundaries based on monitoring results and hazard determinations. 

Vertical laminar flow clean benches also are not BSCs. They may be useful, for example, in hospital pharmacies when a clean area is needed. Although these units generally have a sash, the air is usually discharged into the room under the sash, resulting in the same potential problems as the horizontal laminar flow clean benches. 

The technology in the fume capture field Is not well developed, and performances of many capture systems are low and typically may be in the 30% to 60% range. There is a paucity of fundamental research and development in the fume capture field. In contrast, hundreds of million of dollars have iteen spent on research and development activities in the gas-cleaning area, which is mature and well developed. It is not uncommon to specify and to measure gas-cleaning equipment performances of over 99.9% colleaion efficiency. As shown in Eq. (13.75), the ovcTall fume control system performance is determined by the product of the capture efficiency and the gas-cleaning efficiency. This equation clearly shows the need to improve the efficiency of capture of the fume at the source in order to obtain significant improvements in the overall fume control system performance. 

Clean tunnel A tunnel providing access of operators or production components from one clean area to another. 

All the foregoing has been concerned with the initial protection of steelwork, but there is far more maintenance painting than new work. The same principles apply to maintenance painting, with the exception that it is often only in isolated patches and in complicated situations, such as around flanges, etc. that the steelwork is bare of paint, and then it is frequently heavily contaminated with corrosion products. The first necessity, therefore, is to clean down these areas to bare steel, but often it is not possible to use blasting methods. Often hand cleaning is all that can be done. Careful supervision is needed, and the cleaned areas must be primed without delay and then brought forward with a suitable anti-corrosive system. 

Filtered air may be used to purge a complete room, or it m be confined to a specific area and incorporate the principle of laminar flow, which permits operations to be carried out in a gentle current of sterile air. The direction of the airflow may be horizontal or vertical, depending upon the type of equipment being nsed, the type of operation and the material being handled. It is important that there is no obstruction between the air supply and the exposed product, since this may resnlt in the deflection of microorganisms or particulate matter fiom a non-sterile surface and canse contamination. Airflow gauges are essential to monitor that the correct flow rate is obtained in laminar flow units and in complete suites to ensure that a positive pressure fiom clean to less clean areas is always maintained. 

Clean and aseptic areas must be adequately illuminated lights are best housed above transparent panels set in a false ceiling. Electrical switches and sockets should fit flush to the wall. When required, gases should be piped into the area from outside the unit. Pipes and ducts, if they have to be brought into the clean area, must be effechvely sealed through the walls. Additionally they must either be boxed in (which prevents dust accumulation) or readily cleanable. Alternatively, pipes and ducts may be sited above false ceilings. 

Sinks supplied to clean areas should be made of stainless steel and have no overflow, and the water should be of at least potable quahty. Wherever possible, drains in clean areas should be avoided. If installed, however, they should be fitted with effective, easily cleanable traps and with air breaks to prevent backflow. Any floor channels in a clean area should be open, shallow and cleanable and should be connected to drains outside the area. They should be monitored microbiologically. Sinks and drains should be excluded from aseptic areas except where radiopharmaceutical products are being processed when sinks are a requirement. 

Containers made flxm fibrous materials such as paper, cardboard and sacking, are generally heavily contaminated (especially with moulds and bacterial spores) and should not be taken into clean or aseptic areas where fibres or microorganisms shed flxm them could contaminate the product. Ingredients which must be brought into clean areas must first be transferred to suitable metal or plastic containers. 

Lysimeter assembly and pre-installation testing should be conducted in a clean area, preferably indoors. Careful installation is necessary to ensure proper operation. The components of the lysimeters may need to be decontaminated prior to installation... 

To reduce the accidental spread of hazardous substances by workers from a contaminated area to a clean area, zones should be delineated on the site where different types of operations will occur, and the flow of personnel among the zones should be controlled. The establishment of work zones will help ensure that personnel are properly protected against the hazards present where they are working, that work activities and contamination are confined to the appropriate areas, and that personnel can be located and evacuated in an emergency. 

Delineation of these three zones should be based on sampling and monitoring results and on an evaluation of the potential routes and amount of contaminant dispersion in the event of a release. Movement of personnel and equipment among these zones should be minimized and restricted to specific access control points to prevent cross-contamination from contaminated areas to clean areas. A decision for evaluating health and safety aspects of decontamination methods is presented in Figure 16.22.105... 

At a hazardous waste site, remediation and decontamination facilities should be located in the CRZ, that is, the area between the exclusion zone (the contaminated area) and the support zone (the clean area). The level and types of remediation and decontamination procedures required depend on several site-specific factors ... 

Stations should be separated physically to prevent cross-contamination and should be arranged in order of decreasing contamination, preferably in a straight line. Separate flow patterns and stations should be provided to isolate workers from different contamination zones containing incompatible wastes. Entry and exit points should be conspicuously marked, and the entry to the CRZ from the exclusion zone should be separate from the entry to the exclusion zone from the CRZ. Dressing stations for entry to the CRZ should be separate from redressing areas for exit from the CRZ. Personnel who wish to enter clean areas of the decontamination facility, such as locker rooms, should be completely decontaminated. 

Obtaining soil samples in the cleaned area for analysis, and documenting the effectiveness of the cleanup effort... 

The preventive procedure relies on putting worm-free animals on a parasite-free or a clean pasture. Clean areas may be new leys or can be provided on permanent pasture by alternating with other livestock species not sharing the same spectrum of parasites, or by use of aftermath after harvesting a hay or silage crop (this procedure is generally difficult to apply under practical farming conditions). 

Only start the work if an appropriate fume cupboard, fume hood, glove box or clean area is available. Hazards or contamination dictate where in the laboratory the work can be carried out. 

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