Heating Cooling and Ventilation
The control room, exam (magnet) room, and technical room have three independent systems for heating and cooling.
An air handler in the plant room provides fresh air ventilation for the control room and the technical room. If that does not provide sufficent fresh air, there are openable windows in the control room. Exam room fresh air comes from a Mitsubishi Lossnay mounted above the ceiling of the the control room.
Emergency Extract Fan
Under normal circumstances any helium gas escaping the magnet dewar leaves the exam room through the quench pipe. An oxygen sensor monitors the air in the exam room. If He gas displaces the oxygen, an alarm will sound and the emergency extract fan will switch on automatically.
The fan can be controlled by the override switch pictured above. Auto is the normal operation. Hand turns on the fan. Off switches the fan off even during a low oxygen alarm. Off and Hand should never be used during regular scanner use.
When on, the powerful extract fan creates a strong negative pressure in the exam room. This makes opening the door very difficult. It is possible for a person to become trapped in the exam room while the fan is running. The following procedures are in place to reduce the risk of being trapped.
- Do not unlock the exam room door if there is no key in the override switch.
- Double check the override switch is set to auto before unlocking the exam room door.
- When working alone, you must block the exam room open with a sand bag.
- We highly recommend blocking the door open with a sand bag when working in exam room, even if a Level 1 is present.
- Do not cover or block the wave guides.
When the emergency extract fan activates during scanning:
- Determine why the fan has switched on.
- Do not enter the room until it is safe.
- Do not enter the room unless the door is wedged open.
- Attempt to open the exam room door.
- If the door will not open, have one person briefly turn the fan off while another pulls the door open. As soon as the door is open, switch the fan back to Auto.
- Place a sand bag in the door to prevent it from closing.
- Wait for the air to clear before entering the room. Opening a window may help.
The Mitusbishi Lossnay heat recovery ventilation system works in conjunction with the exam room heating and cooling. Switching the Lossnay off will also switch off exam room heating and cooling. Exam room fan speed is set using the Lossnay control. Fan speeds 1 and 2 are too low for proper operation. Speed 3 is enough for heating and cooling but is marginal for the humidifier. Speeds 1 and 2 are locked out.
An exhaust fan in the technical creates a flow of air over the participant from the front the the bore to the back. The fan speed is adjustable both from the vital screen at the magnet and from the console. Fan speed three is the recommend and minimum speed for most scans. When you start a new exam, the system will automatically set the fan to speed three if was on a lower speed. If you set a lower speed and click on proceed in the warning dialog, the fan will stay there for the remainder of the exam.
The system may suggest a higher fan speed for high SAR scans. If you do not select the recommended higher speed, the scanner may enforce a cool down wait between scans.
See the Instructions for Use for more information.
Heating and Cooling
Three independent systems provide heating and cooling for the exam room, control room and technical room. Controls for the exam room and control room are in the control room at the far left side.
Magnet room air is humidity controlled. The humidifier and humidistat are in the control room closet.