Make sure closed system trigger sprays are validated

1st April 2013

Karen Rossington takes a closer look at the risks of a trigger spray disinfectant delivery system.
Conventionally, disinfectants are delivered by either trigger sprays or aerosols. Trigger spray systems offer significant advantages over aerosols, including an adjustable nozzle so liquid can be dispensed as a jet or a spray. They are environmentally friendly as they contain no propellants, which require special disposal procedures. Also all of the liquid can be dispensed so there is no wastage, making them a cost effective solution compared with an aerosol.
However, there is a significant potential drawback with some trigger sprays, as contaminated air can be drawn back into the bottle compromising the sterility of the liquid. As a result of validation work within a licensed unit, it was identified that a trigger spray alcohol, used to disinfect items, had been contaminated with fungal spores only eight hours after opening. (Contamination Control at your Fingertips, Pharmaceutical Manufacturing International, Autumn 1999)
The SteriShield Delivery System is a validated solution to this problem. The SteriShield Delivery System provides a closed and secure system that preserves and protects the integrity of the contents of a trigger spray bottle throughout use. The possibility of ‘suck back’ associated with conventional trigger sprays, where airborne contamination can enter the liquid, is eliminated.


Is the closed trigger system validated? An MHRA/FDA inspector will expect confirmation of the in-use shelf life of a sterile liquid dispensed in a trigger spray format.
However, not all closed trigger spray systems are the same. Consideration should be given to the validation work carried out.

  • Was the trigger spray tested with nutrient broth as well as the sterile fluid?

  • Was the testing carried out using a sufficient number of samples?

  • Was the test work carried out in a controlled background, cleanroom environment?

  • Did negative controls confirm the original samples were not contaminated?

  • Was the broth viable to the end of the testing?

  • Was the sterility testing carried out by an independent laboratory?

SteriShield delivery system validation

Thirty-two one litre bottles were assembled as per routine production in a Grade C room and filled with Tryptone Soya Broth. The bottles were then irradiated to a minimum of 25kGy. Sterility was confirmed at time point zero, using a method based on the requirements of the USP sterility test. The TSB was also tested to confirm its ability to support microbial growth (fertility test).
After irradiation, the spray nozzles of 24 bottles were opened and 50ml of the TSB expelled from each by performing approximately 25 trigger actuations to encourage any ingress of air. These bottles were then left in the most ‘at risk’ area on the floor of a validated Grade D cleanroom until required for testing. At each time point 1, 2, 4, 8, 13, 26 and 52 weeks, three bottles were removed for sterility testing and the contents of one of these bottles was also used to confirm the continuing fertility of
the TSB.
All sampling was done through the spray nozzle to represent normal use.
Seven further unopened double-bagged bottles were stored within the same cleanroom.
One bottle was tested at each time point for sterility testing as a negative control. All sterility and fertility testing was carried out independently by Isotron Laboratories (Swindon, UK).
To determine the environmental challenge to the SteriShield Delivery System over the course of the trial, environmental monitoring was carried out periodically using active air monitoring.


Not all closed trigger spray systems are the same. Since its introduction, the SteriShield Delivery System has been used widely throughout the world to protect the integrity of sterile alcohols, biocides and neutral detergents in trigger spray presentations.
There has not been a single reported sterility failure in the supply of more than two million bottles fitted with the SteriShield Delivery System.
Robust validation of the system has been carried out using an independent test house, negative and positive controls and a validated background environment.
The use of a nutrient medium, through the spray nozzle sampling in a Grade D cleanroom presented perhaps the greatest challenge possible to a closed system; the ingress of even one microbial cell into the system will result in contamination of the bottle contents and rapid growth.
If the system is compromised by one microbial cell the sterility test result will show growth on the test sample.
However, all test samples showed no growth indicating that the SteriShield Delivery System will protect the sterility of the nutrient medium up to 12 months in use.
Karen Rossington is with Shield Medicare Ltd, Farnham, Surrey, UK.





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