If the fire is reported in apartment 5B, and if the member at the second floor finds apartment 2B just off the staircase, the member should at least check one more door to find a 2A or 2C, then call down to have the line stretched. That way, if the B line of apartments is not found in that area it is quick enough to drop down to the lobby and check the other stairways. This type of stairway layout is called? 382
An isolated staircase, since the members will be isolated from the fire area if they choose the improper stair.