by Larry Gallagher


Environmental


Safety and Environmental Considerations in the Life Sciences Laboratory


I


n life science laboratories and biotech firms, safety and environmental issues can be pre- sented by the gases and cryogens utilized in the processes and controls. From simple oxygen deficiency that needs monitoring and controlling to toxic or flammable gas issues requiring special containment and controls, use of proper equipment and facility designs can ensure a safe working environment.


This article will detail the origins of specific areas that pose challenges and the type of gas systems and equipment that need to be employed to ensure a safe atmosphere for the staff and the work environment. The informa- tion will be presented in two sections. The first deals with the use of cryogenic gases, nitrogen, carbon dioxide, argon, and oxygen, and the second section with hydrogen and certain toxic gases that may also be flammable. Though the use of gases in today’s life science laboratory should always be considered in compliance to all of the regulations and standards that apply, as a whole there are specific hazards and sev- eral specific standards that address the unique properties and hazards of each gas.


Use of cryogenic gases The use of cryogenic liquid nitrogen for its


cryogenic “cold temperature” properties (liq- uid nitrogen boils at atmospheric pressure at –196 °C) has until now been the main reason to use cryogenic liquids in life science labs. Its use in cryopreservation in which biological specimens are frozen with and stored at liquid nitrogen temperatures has grown dramatically in the past 20 years, to the extent that large re- positories supplied with liquid from bulk tanks are placed outside of the building. However, in smaller laboratories there has been equal growth in the number and size of both the freezers that hold the liquid nitrogen and the


Liquid Nitrogen Cylinder


Cryogenic Freezer


Liquid Nitrogen Cylinder


liquid cylinders that supply it. It is not uncom- mon to find four or five freezers with 6–10 liquid nitrogen cylinders in an anteroom or hallway of a life science laboratory. In National Fire Protection Association Code 55, Compressed Gases and Cryogenic Fluids, the minimum re- quired ventilation for specific volumes of gases and cryogens is spelled out, though eventually all of the liquid will convert to gaseous nitrogen in that space. Under normal circumstances, this occurs rather slowly at a rate of perhaps 2–3% of the liquid contents per day.


During transfer operations, however, that rate is dependent on how insulated and how well the supply side of the operation delivers the liquid


577 Series CryoWiz™


Oxygen Deficiency Monitor Input Remote Alarm Output


Ethernet Connection USB Connection


Power Cord, 110 VAC or 220 VAC


Cryogenic Hose, Typical Both Inlets and Outlet


Purge Gas Pipe-Away System Relief Valve Pipe-Away


Oxygen Deficiency Monitor


Dry Nitrogen Supply,


75-100 PSI


in a stable state, as well as how and where the liquid that vaporizes during the transfer is vent- ed. Typically referred to as “hot gas,” because it turns to gas in order to cool down the hoses, piping, and control valves, it can take as much as 25% of what is actually transferred just to cool everything down. When you consider that the liquid-to-gas expansion ratio for nitrogen is 696:1, the volume of resulting hot gas, com- bined with what is normally vented daily, can pose an oxygen deficiency concern, even with acceptable air exchange in the area or room.


If you consider that each liquid cylinder of 230-L volume contains 5000+ cubic feet of gas at stan- dard temperature and pressure and a typical


Liquid Nitrogen Outlet to Freezer Figure 1 – Typical cryogenic freezer setup. AMERICAN LABORATORY • 15 • SEPTEMBER 2014


ø1/2” PVC Water Drain


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