To create sand boxed environments like chroot and schroot or in case of you get the error when installing DEB packages: “wrong architecture i386” you have to execute the following command lines as an administrator in 64bit platforms:
# dpkg --add-architecture i386
# apt-get update
At this point I have installed Debian multiarchitecture to support 32 bit programs. They are gonna be install under 32bit directories as well.

References:
Best example is the Guide Teamviewer.

By default, your system will install packages for your default system architecture.
Before installing programs of another architecture in your system or sand boxed environments like chroot and schroot verify the availability of these in the repositories:
$ sudo nano /etc/apt/sources.list
$ apt-get update
$ apt-cache search nmap
$ apt-cache show nmap
Find the line "Architecture" in the Output.
$ sudo apt-get install nmap:i386

References:
Topic: To create 32bit chroot envronments
Web: http://askubuntu.com/questions/29665/how-do-i-apt-get-a-32-bit-package-on-a-64-bit-installation
File: 64 bit - How do I apt-get a 32-bit package on a 64-bit installation_ - Ask Ubuntu.pdf
