Classifications

Safe SCPs either never or almost never breach. They are extremely easy to recontain and can be generally disregarded when contained.

Euclid SCPs are much more unpredictable than Safe SCPs. They require significantly more effort to recontain and can breach when left alone. All sapient SCPs are automatically Euclid.

Keter SCPs require extra precautions when dealing with them and can easily breach if mismanaged. Recontainment of a Keter SCP is a much harder than the previous two classes.

Pending is the classification given to SCPs that are either uncontained or have too much unknown about them to assign a containment class.

Cannot be contained, it is the containment of other SCPs. Such as SCP-2000 and SCP-3000

SCPs that cannot be contained, even though they pose a significant threat to the human population. Such as the 001 proposal: "When the day breaks"

The SCP has minimal impact on the site. Even when breached, site operations will continue as normal.

The SCP will slightly disrupt site operations. Personnel would likely be forced to stay clear of a hallway or room.

The SCP significantly disrupt site operations to the point where personnel are forced to avoid a sector of the facility. 

The SCP greatly impact site operations to the point where no area in the facility is safe.

The SCP has such a major impact when breached that the SCP foundation puts its highest priority on eliminating it. Humanity is at risk of being extinct.

SCPs in this category pose no significant threat to personnel and are completely safe to handle.

These SCPs can cause mild harm if improperly handled, but pose little threat overall.

These SCPs are able to inflict mild to severe damage to a human being. 

Humans interacting with these SCPs have a very high risk of being affected by such SCP. The effects can cause death or severe trauma.

Interacting with these SCPs will have instant effects. Death is very likely and expected from these SCPs although you are (in rare conditions) able to survive. The recovery from these effects are nearly impossible.