Brussels Airport (BRU) Terminal Map

Passenger Terminal Layout and Transfer Options at Brussels Airport:

The Brussels Airport passenger terminal is a huge building with four levels and two 'Piers' / Concourses A and B.
The basement level houses the Railway Station and the Ground level is for buses and baggage lockers.
Level 2 of the passenger terminal is the Arrivals Level, with tourist information, communication & internet center, Travelex, rental car desks, 'Direct Way' (limo, business & welcome services), Lost & Found, train ticket counter, baggage reclaim areas, airline ticket counters and shops & restaurants.
Level 3 of the passenger terminal is the Departures Level, with check-in counters 1 - 10, security checkpoint, and access to Concourses A & B. A new check-in area caters exclusively to holiday travelers, with special attention to families with children and the elderly.
Level 4 of the passenger terminal is occupied by shops & restaurants, a pharmacy, Kiddiland, meditation room, Regus Sky Port Meeting Center, travel agency Connection, and airline lounges.

Concourse A: Departure level 3 connects directly by elevator to the underground level which in turn connects to Concourse A: Concourse A, ground level after security check-point, offers some shops & restaurants and Gates A28 to A39. The first level also has some shops & restaurants and access to gates A40 to A72 and to gates T61 to T72. At the end of Concourse A is access to the transfer bus to Pier B (B gates) The second level is a service level with some airline lounges.
Concourse B, accessible from the Departure level, houses gates B01-B40 on level 3, and gates B80-B98 on level 0 - from which the transfer bus can take them to the A or T gates.  Pier B is divided into Pier B Departures and Pier B  Arrivals.  

Transfer Options within the passenger terminal: Note that all flights from Schengen countries arrive at A-Gates, and all flights to non-Schengen countries depart from B-Gates (exception: Brussels Airline flights to Africa).

Passengers Arriving from a Schengen country and tansferring to either A, B or T Gates: 
(a) your connecting flight is at A Gate: You arrived at Concourse A and will depart on the same concourse either at level 1 (gates A40-A72) or level 0 (ground level, gates A28-A39).
(b) your connecting flight is at B gate:  At Concourse A follow 'Transfer B' signs to elevator / escalator and go to level; walk through the tunnel & take escalator to level 2; follow signs "transfer B' follow corridor and go through passport control; then take escalator to Level 3, follow corridor to shopping area at start of Concourse B; pass security control and proceed to your gate.
(c) your connecting flight is at T gate:  At Concourse A, follow signs to the T gates towards the end of Concourse A, go through passport control and proceed to your T gate.

NOTE:  A new connector is to be built between Pier A and the main terminal, whereupon travelers can connect on the same level from check-in to either Pier A or Pier B.  Until completion time of the connector building by late 2014, Pier A is still only accessible via underground tunnel.