Leakages are very unlikely if you take care.  However, the most common place for a leakage it to occur is at the connection points such as the regulator, valve or hose. Check your equipment regularly and particularly before use, for any signs of damage, wear or deterioration, and to identify any missing items. 
It is important that if you suspect a leak you act quickly. Open all doors and windows, don't use a naked flame or smoke and don't turn electrical equipment on or off.  The best course of action is to attempt to stop the leak by closing the valve and replacing the bung or cap. 
If the leak cannot be stopped and it is safe to do so, the cylinder should be carefully removed to a well-ventilated open space, clear of drains, buildings, sources of ignition and other LPG cylinders.  The Calor cylinder should, if possible, be marked 'faulty' and left with the leak (usually at the valve) uppermost.  Contact your local Calor supplier to arrange collection of the Calor cylinder. If assistance is needed from the Fire Services please tell them of the presence of LPG.

CO is an invisible gas which you cannot smell, taste or see. If gas appliances are t  installed and used correctly with adequate ventilation and flueing , and regularly maintained, the risk of CO poisoning is virtually nil.   Accidents which have occurred as a result of CO poisoning or asphyxiation are caused by a combination of circumstances, including inadequate ventilation, unsatisfactory flueing, poor appliance performance, user interference or lack of routine maintenance.
IMPORTANT: If you think your LPG appliance is producing CO, switch it off, open all windows and doors and leave the room to ventilate before getting it checked by a CORGI registered installer. If you are feeling unwell, seek medical advice immediately.