Modern stored pressure fire extinguishers have a few crucial components which could spell disaster if failing when you need to use it to extinguish fire.
Without proper checks or "a suitable system of maintenance" prescribed in Article 17 - The Regulatory Reform (Fire Safety) Order 2005, such internal damage or deterioration is easily missed.
These two images, from two different extinguisher manufacturers, shows the plastic composition breakdown of the dip tube connection assembly. The result when activated? Well, a disappointing hiss! And what about the event of emergency? Sadly, your fire is still growing...
Make sure your equipment is maintained by a BAFE approved company, keeping it functional for when you might need it.