Integrity of s eals 
 The integrity of sealing of ampoules should be assessed 
on an individual basis. Two techniques are available that 
depend on dye ingress under vacuum or electronic 
means. With dye intrusion, the ampoules are submerged 
in a dye solution and under an applied vacuum. Any 
container that has cracks in its structure or is not sealed 
will admit the dye when the vacuum is reduced. On 
washing, badly sealed ampoules will be coloured. This 
technique underestimates the problem of bad sealing. In 
the alternative technique, high - frequency spark testing, 
the presence of a leak causes a change in a high - frequency 
electrical signal placed across the ampoule. The method 
is limited to aqueous products with a high conductivity. 
It is a very sensitive technique and detects weak seals not 
detected by the dye test. In reality, both tests should be 
used in parallel.