148
Appendices
Model 335 Temperature Controller
Liquid helium and liquid nitrogen are potential asphyxiants and can cause rapid suffoca-
tion without warning. Store and use in area with adequate ventilation. DO NOT vent con-
tainer in confined spaces. DO NOT enter confined spaces where gas may be present unless
area has been well ventilated. If inhaled, remove to fresh air. If not breathing, give artifi-
cial respiration. If breathing is difficult, give oxygen. Get medical help.
Liquid helium and liquid nitrogen can cause severe frostbite to the eyes or skin. DO NOT
touch frosted pipes or valves. In case of frostbite, consult a physician at once. If a physi-
cian is not readily available, warm the affected areas with water that is near body tem-
perature.
The two most important safety aspects to consider when handling LHe and LN
2
are
adequate ventilation and eye and skin protection. Although helium and nitrogen
gases are non-toxic, they are dangerous in that they replace the air in a normal
breathing atmosphere. Liquid products are of an even greater threat since a small
amount of liquid evaporates to create a large amount of gas. Therefore, it is impera-
tive that cryogenic Dewars be stored and the MTD system be operated in open and
well ventilated areas.
Persons transferring LHe and LN
2
should make every effort to protect eyes and skin
from accidental contact with liquid or the cold gas issuing from it. Protect your eyes
with full-face shield or chemical splash goggles. Safety glasses (even with side
shields) are not adequate. Always wear special cryogenic gloves (Tempshield Cryo-
Gloves® or equivalent) when handling anything that is, or may have been, in contact
with the liquid or cold gas, or with cold pipes or equipment. Long sleeve shirts and
cuffless trousers that are of sufficient length to prevent liquid from entering the shoes
are recommended.
B.5 Recommended
First Aid
Every site that stores and uses LHe and LN2 should have an appropriate Material
Safety Data Sheet (MSDS) present. The MSDS may be obtained from the manufac-
turer/distributor. The MSDS will specify the symptoms of overexposure and the first
aid to be used. A typical summary of these instructions is provided as follows.
If symptoms of asphyxia such as headache, drowsiness, dizziness, excitation, excess
salivation, vomiting, or unconsciousness are observed, remove the victim to fresh air.
If breathing is difficult, give oxygen. If breathing has stopped, give artificial respira-
tion. Call a physician immediately.
If exposure to cryogenic liquids or cold gases occurs, restore tissue to normal body
temperature (98.6 °F) as rapidly as possible, then protect the injured tissue from fur-
ther damage and infection. Call a physician immediately. Rapid warming of the
affected parts is best achieved by bathing it in warm water. The water temperature
should not exceed 105 °F (40 °C), and under no circumstances should the frozen part
be rubbed, either before or after rewarming. If the eyes are involved, flush them thor-
oughly with warm water for at least 15 minutes. In case of massive exposure, remove
clothing while showering with warm water. The patient should not drink alcohol or
smoke. Keep warm and rest. Call a physician immediately.
