I went to Walmart and bought a Kitchen type smoke detector with the silence button. I removed the one PC installed behind the A/C and placed the new one up front in the ceiling in line with the DVD player. Every time my wife would cook on the stove the original one would go off and it did not have the silence button. Now she has to burn something to get it to go off and the button stops the alarm for a few minutes.
The CO2 is build into the LP detector under the passenger side bed. CO2 can be mounted either on the ceiling or the near the floor. Smoke on the ceiling and LP near the floor. Stuart should have told you this.