Good for you for recognizing that anyone living in a multi-story home should have at least one escape ladder. The number of ladders required depends largely upon the configuration of your home.
The larger the home and the greater the distance between the bedrooms, the more likely additional ladders are appropriate. The other critical factor is the location of the stairs because their propensity to act as a natural flue. If bedrooms are located on either side of the stairs, then escape ladders should be provided on either side as well since fire and smoke racing up the stairs may prevent you crossing from one room to the other.
The concept of the stairs acting as a flue should also influence your decision as to which bedroom is assigned to which child. Ideally, infants’ and toddlers’ bedrooms should be on the same side of the stairwell as the parents’ bedroom. Older children who are capable of deploying an escape ladder may have bedrooms on the other side of the stairwell.
The type of escape ladder to provide is the next appropriate question. A ladder built into the wall beneath the window or bolted to the floor below the window are the best options since they will be the easiest to deploy. Portable ladders are okay, but they may not be where you expect them in the event of an emergency. Over time, portable ladders frequently get buried under the bed or in a closet or relocated by another family member.
Whichever type of ladder you obtain, practice at least once with it to make sure it is fully assembled and will work in your particular situation. Older children whom you expect to operate the ladder independently should practice doing so at least once a year. Don’t forget to agree upon a family meeting point a safe distance from the house.
A reminder to those who are "baby proofing" their windows to prevent a toddler from falling out, be sure to use hardware or gates that can be readily removed by an adult in the event of an emergency.
While we are on the subject of fire safety be sure to have at least one fire extinguisher on each level of the home. Again, mounting the extinguisher to the wall (in a closet or cabinet) will ensure you will know where to find them in the event of an emergency. Finally, make sure your smoke detectors have fresh batteries, are less than ten years old and are located in each bedroom, in the adjacent hallway and on each level of your home.