The Orientation filmstrip makes cryptic reference to an incident that occured sometime in the past:  

Not long after the experiments began, however, there was an incident. And since that time the following protocol has been observed: every 108 minutes the button must be pushed. From the moment the alarm sounds you will have 4 minutes to enter the code into the microcomputer processor [splice] induction into the program. When the alarm sounds, either you or your partner must input the code. It is highly recommended that you and your partner take alternating shifts. In this manner you will stay as fresh and alert [splice] utmost importance that when the alarm sounds the code be entered correctly, and in a timely fashion. Do not attempt to use the computer [splice] for anything [splice]. Congratulations, until your replacements arrive, the future of the project is in your hands. On behalf of the DeGroots, Alvar Hanso and all of us at the Dharma Initiative, thank you. Namaste. And good luck.

However, the information about the "incident" is incomplete at best. The filmstrip appears to be spliced at the moment that explains what happens after one enters the numbers into the computer, and before an explaination as to what the alarm means, or what will happen in the event that the code is not entered. The second edit of the filmstrip does not further explain the significance of the "incident;" it only warns the operator to not use the computer for communication purposes.

According to Kelvin, the hatch is built on an area that is geologically unique in its electromagnetism. The incident occured when there was a "leak," and now the charge builds up to dangerous levels. By entering the numbers every 108 minutes, the electromagnetic charge is dispersed before it can become a threat.