so I installed the basic baggage scanner (the big black one) into my baggage handling system. it seems to work fine and regularly takes bad bags out of the system. I then unlocked the specific baggage scanners (the small white ones), and their description said something like “your second line of defense”, so i assumed they would take out even more ba baggage. I installed one of each kind into the system, immediately after my big baggage scanner, and waited. However, over the course of about 1 and a half in-game days, at an airport that sees 38 flights a day, these scanners too out not a single bag.
so my question is this: do you need these scanners, or even the third tier one where a security guards searches each bag, or is it fine to just have the single generic one?
Yes, Alpha 34 will bring sense to this. The first scanner clears out anything that might get detected by second line scanners, the second line scanners clear out bags with specific content that may get detected in the third scanner. The third scanner is manually operated and thoroughly scans baggage passing through and, if the security officer is productive enough, either successfully detects a harmful bag or misses it or routes it as a false positive.
The rating system takes this into account, so your total security rating is made up of (amongst a few other ratings) your tier I score, tier II score and tier III score. This is explained in the UI, but in short:
Bags that are scanned in tier I correctly should not be scanned in tier II and III, and so forth (i.e. cleared in tier II should not be scanned in III) as this will degrade your rating.