Mike,
Standard compression fitting are not designed for high pressure work. The brass nuts and olives split overtime.
I once worked on a plant where these fittings where used on high pressure steamlines(less than the pressure of a t/m). We spent many days replacing them due to them splitting.
I am in the process of changing most of mine, as the standard brass connections are splitting due to pressure.
The mild steel "ISO B series", which the standard connections are can be purchased from RS Components, they are the best rated for high pressure. Most carpet cleaning connectors are brass, and as stated are not suitable for high pressure. Also from rs you can buy plastic dust protectors which help when the ends are not in use.