Another option for larger quantities is a dewar. Dewar containers can hold liquid nitrogen, argon, oxygen, CO2, etc. A 180 liter dewar may hold 140 cubic meters at 10 bar. The disadvantage of liquid nitrogen is that it is a perishable commodity.It will vaporize and escape from the dewars over a short period of time. It may all be gone in 3 weeks if the dewar is in the hot sun.Portable dewars come in many sizes from the little 1 liter size that the dermatologist might use to 265 liters.nother option for larger quantities is a dewar. Dewar containers can hold liquid nitrogen, argon, oxygen, CO2, etc. A 180 liter dewar may hold 140 cubic meters at 10 bar. The disadvantage of liquid nitrogen is that it is a perishable commodity.
One way to achieve that is using earplugs. Earplugs are a popular solution for blocking or lowering the volume of incoming noise and for protecting the ear from dangerous sound environments such as rock concerts or heavy machinery. However, many people use them during the night to help secure a good night sleep. While earplugs are quite useful, their application should be treated with care as they can cause problems including discomfort and inconvenience, and in rare cases, issues such as inner ear infections, tinnitus and hearing loss.
The simplest and least expensive means of preventing problems associated with acoustic noise during MR procedures is routinely use disposable earplugs or headphones. Earplugs, when properly used, can abate noise by 10- to 30-dB, which is usually an adequate amount of sound attenuation for the MR environment. The use of earplugs typically provides a sufficient decrease in acoustic noise that, in turn, is capable of preventing hearing problems.