• Object ID: 00000018WIA30320870GYZ
  • Topic ID: id_40025838 Version: 1.9
  • Date: Jul 26, 2022 1:18:38 PM

Quench with vent failure

About this task

A magnet quench can result in the release of cryogen vapor into the magnet room if the vent fails; white clouds of vapor appear in the magnet room. Cryogens released during a quench can cause asphyxiation, frostbite, or injuries due to panic. Magnet quenches are indicated by a loud noise, warning message, or the tilting of an image on the image screen. It is critical to have a well-planned method to quickly remove the patient and all personnel from the magnet room if a quench should occur.

These magnets contain approximately 1950 liters of liquid helium:

  • 1.5T

If 100% of the 1950 LHe fills the minimum sized scan room, a properly functioning emergency exhaust fan with 1200 CFM and 12 scan room air exchange / per hour would evacuate that minimum sized scan room in about 2 hours. After that time it would be assumed safe for a qualified GE field service engineer to enter the scan room and measure the O2 levels. It remains the customer responsibility to approximate the time to evacuate 1850 LHe for use in the site specific emergency procedures.

Use your site specific magnet room evacuation procedure. The following steps are guidelines for a site procedure in case of a sudden cryogen release into the magnet room.

Step-by-step instructions

  1. Do not panic.
    • Staying calm helps you remain focused so you are able to safely remember and follow your site planned method of action.
  2. Using the intercom, tell the patient to stay calm and remain on the table.
    • Tell the patient that someone will be in shortly to offer assistance.
  3. Turn on the magnet room exhaust fan.
    • The exhaust fan is designed for 1200 cubic feet per minute, which exchanges the total volume of air in the room 12 times per hour. The time for the helium to be near a safe level is based on the amount of helium within a magnet,
  4. Prop open the door between the operator room and hallway or if in a mobile unit, open the door to the outside.
    • This promotes air circulation.
  5. Prop open the door to the magnet room.
    • If the magnet room door does not open, follow your site specific emergency procedure to open the door.
  6. Enter the magnet room and assist anyone present to exit from the room.
    • If a gurney or wheelchair is needed to remove the patient, make sure it is a non-ferrous type.
    • When exiting, stay near the floor where the oxygen will be and immediately exit the magnet room.
  7. Close the MR scan room door when all have been evacuated.
    • If the magnet room door is left open, there is a potential that helium gas will spread to other areas, including heating and cooling vents.
  8. Evacuate all personnel from the area until the air is restored to normal.