Safety screens

Caution The preparation of methylenecyclopropane must be carried out in an efficient hood because ammonia is evolved. The preparation and handling of oxaspiropentane should be carried out behind a safety screen. 

Caution This reaction should be carried out behind a safety screen. 

This experiment must be carried out in an efficient hood since diazomethane is highly toxic. Also, a safety screen is recommended. (See Chapter 17, Section III for other precautions.)... 

Caution Selenium compounds are exceedingly toxic (Note 1). Hydrogen peroxide attacks the skin and may decompose violently (Note 2). The reaction should be carried out behind a safety screen and in an efficient fume hood, and the operator should wear safety glasses and rubber gloves. 

Fig. 5.1a shows the slurry packing system that 1 use. This operates at a fairly low pressure, as I am not especially interested in producing columns with very high efficiencies, but rather in saving on the cost of commercial columns. The pump and high pressure valve are rated for pressures of 500 bar (7500 psi) and 400 bar (6000 psi) respectively. The slurry reservoir is a stainless steel tube 85 cm long, with a capacity of about 50 cm3. The method is not hazardous unless there is air trapped in the high pressure line nevertheless it is advisable to use a safety screen. 

Careful attention to such detail is necessary as a second line of defence against the effects of reactive hazards. The level of protection considered necessary may range from the essential and absolute minimum of effective eye protection, via the safety screen, fume cupboard or enclosed reactor, up to the ultimate of a remotely controlled and blast-resistant isolation cell (usually for high-pressure operations). In the absence of facilities appropriate to the assessed level of hazard, operations must be deferred until such facilities are available. 

During optimisation of a preparative procedure, heating mixtures of 4-chloroaceto-phenone and dimethylamine (4.22 1) at 234°C led to two explosions. Use of a safety screen is advised. 

Hydrosilylation with 2,4,6,8-tetramethylcyclotetrasiloxane has sometimes given uncontrollable exotherms or explosions in the laboratory. Use of safety screens and the lowest possible (<20 ppm) level of platinum catalyst are recommended. See VINYLSILOXANES... 

In demonstrating the use of powdered aluminium to reduce the oxide in a thermite-type reaction, the mixture must be heated behind a safety screen because of the small explosion produced [1]. Consolidation of the thermite mixture into a high-density composite gives chemical heat sources which are safe to handle [2],... 

Caution This reaction should be carried out behind a safety screen. The solvent removal and product distillation steps should also be carried out behind a screen to minimize danger due to contamination of the product with undetected peroxides. 

The description of the method to be used should include details of all practical precautions which will be taken to limit risk, such as the need for ventilation, minimization of inhalation of particulates or aerosols, using fume cupboards or safety screens, and wearing gloves, laboratory coat, and safety spectacles. Handling procedures, packaging for transit, and disposal of unused reactants or products all need to be considered. 

All reactions employing diazomethane must be carried out in a well-ventilated hood behind a safety screen. After observing the appropriate precautions, diazomethane is safely prepared by the base treatment of N-methyl-N nitroso-p-toluene sulphonamide ( Diazald ). 

If no immediate hazards are identified during the approach to the site, the incident commander will likely approve the team to enter the site and perform the site characterization. During this stage, the team will continue field safety screening at the site and conduct a detailed site investigation. 

The appropriate level of personal protection necessary to safely perform the site characterization activities will depend on the assessment of site hazards that might pose a risk to the site characterization team. The hazard assessment may be further refined during the approach to the site, based on the results of the field safety screening and initial observations of site conditions. Two general scenarios are considered, one in which there are no obvious signs of immediate hazards, and one in which there are indicators of site hazards. 

Two types of kits are discussed in this section, sample collection kits and field test kits. Sample collection kits will generally contain all sample containers, materials, supplies, and forms necessary to perform sample collection activities. Field test kits contain the equipment and supplies necessary to perform field safety screening and rapid field testing of the air, water, and/or soil. Sample collection kits will generally be less expensive to construct than field test kits. Sample collection kits can be pre-positioned throughout a system, while the more expensive field kits may be assigned to specific site characterization teams or personnel. 

The analytical use of the alloy to reduce nitrates is usually accompanied by the risk of a hydrogen explosion, particularly if heating is effected by flame. Use of a safety screen and flameless heating, coupled with displacement of hydrogen by an inert gas, are recommended precautions [1]. The explosion was later attributed to gas pressure in a restricted system [2],... 

Source Johnson DE. Predicting human safety screening and computational approaches, Drug Discovery Today 5 445 54 (2000). 

Owing to the possibly explosive nature of the ester, the distillation was conducted behind a safety screen, using a water bath for the heat source and keeping the pressure as low as convenient. 

Caution The preparation and distillation of the oxazirane, like that of any active oxygen compound, should he carried out behind a safety screen. 

The procedure described here for the preparation of peroxy-trifluoroacetic acid in methylene chloride has been carried out by the submitters several hundred times without incident and is believed to be the best available. However, it has been pointed out that suspensions of 90% hydrogen peroxide in methylene chloride can be detonated by impact under certain conditions. Accordingly, the use of the recommended safety screen is imperative, and the preparation should not be scaled up without special precautions. The homogeneous solution of peroxytrifluroacetic acid, once obtained, is undoubtedly much safer to handle than the suspension of hydrogen peroxide in methylene chloride. The latter suspension is not transferred, however, and exists for only a brief time period during the preparation. 

Berghmans S, Butler P, Goldsmith P, Waldron G, Gardner I, Golder Z, Richards FM, KimberG, Roach A, Alderton W, Fleming A (2008) Zebrafish based assays for the assessment of cardiac, visual and gut function-potential safety screens for early dmg discovery. J Pharmacol Toxicol Methods 58 59-68... 

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