National Safety Month 2008

Nitrogen is an inert, colorless, odorless, non-corrosive, non-flammable, and extremely cold gas. Although it is nontoxic, it can act as an asphyxiant by displacing oxygen in the air to levels below the required threshold to support life. At extreme cold temperatures (77K-63 K), nitrogen becomes a cryogenic liquid. In its liquid state it can cause severe burns and blisters to human tissue. So in order to prepare ourselves to address the risks associated with using liquid nitrogen, it is crucial to understand what Personnel Protective Equipment (PPE) to wear and what to do when a gas cylinder malfunctions in our research laboratories. To achieve this we must first understand the cylinder that carries liquid nitrogen. It comes in an insulated, vacuum-jacketed pressure vessel. These containers operate at pressures up to 350 psig and have capacities between 80 and 450 liters of liquid. The diagram below will illustrate the layout of the cryogenic tank.

Notice the top view of the diagram on the right hand side. The two cylinder tops in this diagram show the most common cylinders used for liquid nitrogen. Become familiar with the vent valve and the pressure gauge. Look to see if these parts are in working order. Clean ice off the valves if it starts to build-up. If the tank starts to vent, this a normal occurrence to handle increased pressure, but if it starts to rapidly vent, there are some precautionary measures to take.

PORTABLE   ELECTRIC  SPACE  HEATERS

Portable electric heaters manufactured after 1991 include many new performance requirements to enhance safety. For portable electric heaters that may present a fire hazard when tipped over, a tip-over switch will turn the heater off until it is turned upright again. New heaters also include indicator lights to let users know that the heater is plugged in or is turned on. Some manufacturers have included technically innovative safety controls such as infrared or proximity sensors, which can turn a heater off when objects come too close, or when children or pets are near. These kinds of controls may prevent burn injuries to children who might play too near a heater, or reduce the risk of ignition of combustible materials that could contact the heater. The following is a list of safety measures to keep in mind when using an electrical space heater.

• Use heaters on the floor. Never place heaters on furniture, since they may fall, dislodging or breaking parts in the heater, which could result in a fire or shock hazard.
• Unless certified for that purpose, do not use heaters in wet or moist places, such as bathrooms; corrosion or damage to parts in the heater may lead to a fire or shock hazard.
• Do not hide cords under rugs or carpets. Placing anything on top of the cord could cause the cord to overheat, and can cause a fire.

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