Explosibility airborne concentrations

Polyurethanes. These polymers can be considered safe for human use. However, exposure to dust, generated in finishing operations, should be avoided. Ventilation, dust masks, and eye protection are recommended in foam fabrication operations. Polyurethane or polyisocyanurate dust may present an explosion risk under certain conditions. Airborne concentrations of 25—30 g/m are required before an explosion occurs. Inhalation of thermal decomposition products of polyurethanes should be avoided because carbon monoxide and hydrogen cyanide are among the many products present. 

Observe normal precautions appropriate to the circumstances and quantity of material handled. Eye protection is recommended. Heavy airborne concentrations of dust may present an explosion hazard. 

Hazard Zone For an incident that produces an outcome such as toxic release, the hazard zone is the area over which the airborne concentration equals or exceeds some level of concern. For a flammable release, the area of effect is based on a specified level of thermal radiation. For a release that resnlts in explosion, this is the area defined by specified overpressure levels. 

Unfortunately, cold cleaning cannot be a process in which zero energy is added. Although the deaning solvent is not to be heated, it may be necessary to provide cooling in order to control its airborne concentration in the workplace to meet two requirements (1) less than 25 percent of the lower explosive hmit (LEL), and (2) as dose as possible to the 8-hour exposirre limit. 

Engineering Controls Use explosion-proof ventilation equipment. Facilities storing or utilizing this material should be equipped with an eyewash facility and a safety shower. Use adequate ventilation to keep airborne concentrations low. Exposure Limits ... 

As discussed in Chapter 4, chemicals can be a nuisance or pose health risks if they become airborne as a result of inadequate process control, operation and maintenance malpractice, inadequate maintenance, incomplete understanding of the process etc. Hazards may arise if the oxygen concentration in the air fluctuates beyond its normal level of 21% by volume, and fire/explosion dangers may arise from the presence of flammable gases, vapours or dusts in the atmosphere. Thus air quality tests may be required for a variety of purposes such as ... 

Dust explosions occur when finely divided combustible solids are airborne in sufficient concentration and when they are subjected to an ignition source of sufficient energy - provided the oxygen level is sufficiently high. 

Dust must be airborne If a layer of dust on a surface is ignited, the burning process will be relatively slow, releasing heat over a long period of time. However, if a sufficient concentration of finely divided dust particles are suspended in air and ignited, because of the availability of oxygen around each particle, the combustion process will be very rapid giving rise to a dust explosion. 

IDLH Immediately Dangerous to Life or Health levels indicate that exposure to the listed concentrations of airborne contaminants is likely to cause death, immediate or delayed permanent adverse health effects, or prevent escape from the contaminated environment. IDLH levels are established to ensure that the worker can escape from the contaminated environment in the event of a failure of respiratory protection. An indication of "10% LEL" indicates that, for safety considerations, the IDLH was based on an atmospheric concentration of ten percent of the lower explosive limit even though toxicological impacts might not appear until higher concentrations are reached. 

Airborne dust, if present in sufficient concentration in a confined space, can cause a disastrous explosion in the presence of oxygen and an ignition source. Every year about 30 explosions are attributed to grain dust, taking the lives of several workers and causing major losses of property. Barham and Barham (1980) were awarded a pat-... 

This type of fan should not be used in corrosive or explosive environments, since the motor and bearings cannot be protected. Applications where concentrations of airborne abrasives are present should also be avoided. 

Most powders and dusts found in industry can explode when mixed with the right amount of oxidant. For a dust cloud to explode dust must be explosible and airborne dust cloud must be present in an atmosphere capable of supporting combustion and in contact with an ignition source of sufficient energy size distribution of airborne particles must be capable of supporting flame propagation concentration of dust particles must be between the Lower Explosibility Limit (LEL), typically 20 to 100 g m, and Upper Explosibility Limit (UEL), typically in excess of 2000 g m. ... 

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