Working surfaces, safe

Work Surfaces. All horizontal work surfaces (bench tops, containment cabinets or fume hoods) should be protected with impervious material to prevent contamination of the work surfaces with chemical carcinogens. One of the systems that has proved useful is to use the dry, absorbent polyethylene-backed paper (Benchkote, VWR Scientific Co., Cat. No. 52855 , Continuous Sheet Type, Scientific Products Co., Cat. No. P1180). Following contamination, or upon completion of an experiment, or at the end of the day, this protective cover can be rolled up, packaged for safe removal, and disposed of in an appropriate manner. 

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Getting to and from a scaffold working surface is a critical event for your employees. This is the time most scaffold accidents happen. The previous scaffold standard only required that an access ladder or equivalent safe access be provided. ... 

The employer shall determine if the walking/working surfaces on which its employees are to work have the strength and structural integrity to support employees safely. Employees shall be allowed to work on those surfaces only when the surfaces have the requisite strength and structural integrity. 

Decks and other working surfaces shall be maintained in a safe condition. 

Workstations should be arranged so that work may be done safely and comfortably. The worker should be at a suitable height relative to the work surface and there should be no need for undue bending and stretching. Workers must not be expected to stand for long periods of time particularly on solid floors. A suitable seat should be provided when a substantial part of the task can or must be done sitting. The seat should, where possible, provide adequate support for the lower back and a footrest provided for any worker whose feet cannot be placed flat on the floor. It should be made of materials... 

Most of the chemical fume hoods considered here consist of a cabinet or enclosure set at waist level (above a table or storage cabinet) that is connected to a blower located above the hood or external to the hood through a duct system. The cabinet has an open side (or sides) to 2illow a user to perform work within. A movable transparent sash separates the user from the work. Most chemical fume hoods have a sill that functions as an airfoil at the work surface below the sash. The connection to the blower might be by use of a v-belt, or it may be direct drive. This allows provision of a smooth flow of air with minimal turbulence. In some installations, axially mounted blowers are used, especially if multiple hoods are ducted into a common blower. Baffles located in the rear of the cabinet provide control of the air flow patterns, and can usually be adjusted to provide the best air flow around the experiment or procedure being performed. Many chemical fume hoods are equipped with air flow indicators, low flow monitors and alarms, and differenti2d pressure sensors to allow the user to operate safely. The major types of chemical fume hoods include the standard/conventional, W2dk-in, bypass, variable air volume, auxiliary air, or ductless types. Additional types include snorkels and canopies that are portable. Each type must be understood to be operated most efficiently within specifications (see the section below on safe operation). 

Additional hazards of exposure to aerosols are created when liquid drops from a pipet to a work surface (474), when cultures are mixed by alternate suction and expulsion (209, 350, 499), when an inoculum is forcefully ejected onto a culture dish, or when the last drop is blown out (113, 209). It has been demonstrated by high-speed photography that an aerosol of approximately 15,000 droplets, most under ten micrometers in diameter, is produced when the last drop of fluid in the tip of a pipet is blown out with moderate force (Figure 1.1). While the aerosol hazard associated with pipetting procedures can only be reduced by use of safe techniques and use of biological safety cabinets (240), the potential hazards associated with oral ingestion can be eliminated by use of mechanical pipetting aids (426, 428). 

In addition to the convertible Type A cabinet used in the Type B mode, there are two additional versions of the Class II Type B cabinet. These units differ from the Type A and B3 units mainly in the airflow velocities and proportion of air recirculated, as well as in certain other performance specifications. Class II Type B1 cabinetry allows a little more flexibility in working with volatile, toxic, or radioactive substances, since its exhaust is connected to an exhaust duct that exhausts the cabinet air directly outside the building (Figure 9.6). Because 70 percent of the circulating air in the cabinet is exhausted to the outdoors, most nonexplosive or nonflammable chemicals may be used safely in low concentrations. Microgram quantities of toxic, carcinogenic, or radioactive compounds may be handled in the Class II Type B1 cabinet, provided that the work is performed in the direct exhaust portion (behind the smoke split) of the work surface. 

Observe ergonomic guidelines which are ways to arrange your work area to be safe and efficient. For example, use rubber floor mats for standing by a fixed operation adjust the table or working surfaces for your particular height and abilities. 

Ensure all walking-working surfaces are maintained safely. 

A special mention is in order of high-resolution electron microscopy (HREM), a variant that permits columns of atoms normal to the specimen surface to be imaged the resolution is better than an atomic diameter, but the nature of the image is not safely interpretable without the use of computer simulation of images to check whether the assumed interpretation matches what is actually seen. Solid-state chemists studying complex, non-stoichiometric oxides found this image simulation approach essential for their work. The technique has proved immensely powerful, especially with respect to the many types of defect that are found in microstructures. 

An application of transport and compartment-type models to hazard analysis is described in the paper by Honeycutt and Ballantine (19). The compound CGA-72662 running off from agricultural areas into surface waters was modeled in order to set safe application procedures consistent with the protection of aquatic environments. Patterson, et al (2 0) have adapted the UTM model to a software package that is generally applicable to fate assessments of toxic substances in air, water, soil and biota. Their work, now in working draft form, is being used by Dr. William Wood and Dr. Joan Lefler in the Office of Toxic Substances of the U.S. Environmental Protection Agency. 

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