From the manual:

IGNORE_PASSABLE
A7.2 LC
Ignores entities with the PASSABLE flag; to be combined with SCAN_ENTS.

IGNORE_FLAG2
A7.2 LC
Ignores entities with FLAG2; to be combined with SCAN_ENTS.

Further:
"To prevent that a scanning entity triggers itself, set IGNORE_ME.
To ignore a certain entity, set me or you to the entity pointer."


Hope this helps.

no science involved