"Dave Liquorice" wrote in message
ll.net...

Maybe the guidelines regarding installation and/or inspection mean that
bad installations are very rare. ducks

There are many unvented cylinders poorly installed by cowboys. 90% of these
unvented cylinder will not be tested each year as they should be. When they
get old and the valves fail, then expect booms - probably in 10, 20 years
time,a few a year.