You'll need to execute chef client with an alternative configuration. The default config file and directory is /etc/chef/client.rb. You could use that one for one of the nodes / environments. Let's assume that will be "staging". You should probably make sure the node and environment are set up for the proper values:
The other you could create such as /etc/chef/qa/client.rb for your qa configuration. In order to avoid conflict, you'll need to change the various configuration values for Chef that point in /etc/chef, and /var/chef.
See the Chef Configuration Settings wiki page for a complete list of configuration settings you can modify.
You should use the node_name and environment values similar to the staging environment. When you run chef, specify the alternative configuration file.
chef-client -c /etc/chef/qa/client.rb