An airwall is a mesotech application allowing an airlock to be open to space without loss of air-pressure. It is a sheet of connected mesobots (more rarely nanobots) several centimeters thick for redundancy. It can hold an atmosphere against the vacuum of space while allowing properly suited people or spacecraft to pass. It does this via a system of processors in the airwall communicating with compatible processors in the outer layer of a spacesuit or a spacecraft's hull. The effector mesobots recognize the processors in the suit/ship as being authorized to pass and move aside while maintaining a seal with the edge of the suit/ship to prevent air loss. The process of passage is fairly slow but faster than waiting for an airlock to cycle. Airlock doors are still used when the airlock is not in use to protect against radiation, micro-meteors etc.
Airwalls can be considered to be a form of specialized and rugged utility fog. Their strength is approximately that of thick wood - a bioid or vec can lean on the airwall, but high velocity projectiles will go through it and a ramming vehicle will break through and likely damage it.
Many orwoods and other dyson tree types use airwalls to cover part, or all , of their structure and foliage.
Specialised airwall foglets are used in Niven Cloud or Smoke Ring megastructures to prevent atmosphere loss.