What is the difference between a Bowie Dick and Helix test?

The Helix tester is aimed more at testing the effectiveness of air removal and steam penetration of hollow instruments and the Bowie Dick pack test is aimed more for testing the effectiveness of steam penetration on large porous loads


Helix test

A Helix test is made of a tube 1.5 m long and 2mm in diameter. At one end of the tube is a housing for a chemical indicator strip. When a test cycle is run the air must be removed from the tube and steam penetrate all the way through to the indicator and be there for 3.5mins at 134oC for the test to pass. 

Browne Bowie Dick pack test with a before and after example


A Browne Bowie Dick Pack test is a unique combination of advance Browne intelligent ink technology and the original Bowie Dick concept. The Bowie Dick Pack has 198 pieces of recycled newsprint on either side of the chemical indicator sheet. A successful test confirms that steam penetration into a test pack is rapid and even and, by implication, that air and other non-condensable gases have been effectively removed. The chemical indicator sheet at the centre of the pack shows a defined colour change from yellow to dark blue/purple when exposed to a specific combination of time, temperature and steam

Bowie Dick PACK - Key requirements of the BARRIER SYSTEM

Sufficient porosity to allow steam to penetrate. Sufficient density so that once steam entering and air trapped in the pack remain there. The ability to hold the steam or air is extremely important. Holding steam allows for condensation to occur in the pack, which is fundamental to the sterilization process. The condensate will also help to hold any air in the pack so aiding detection. Please note that the condensation  process is important for the absorption of steam by the test pack. Sufficient insulation so that air trapped in the pack is not heated too quickly, as this could give a false result. Sufficient mass to attract the steam. Steam must be attracted to the pack in order for the Bowie Dick test to function.


Fun Fact!

The original test pack was developed in England by Dr. J. Bowie and Mr. J. Dick and was first published in the 'Lancet' journal in 1963. Since that time, the 'Bowie-Dick' type test pack has been widely used and is recognized as a valuable means of monitoring the air removal efficiency of pre-vacuum and vacuum pressure pulse Steam sterilizers. The original test consisted of 29-36 huckaback type towels, each folded and stacked to a height of 10 -11 inches. A sheet of paper with chemical indicator tape (applied in the pattern of a St. Andrew's cross) was placed in the center of the towel stack. The towel stack was then placed inside a metal dressing casket or equivalent container.

Due to the lack of available materials originally specified for the Bowie-Dick type test pack, alternate configurations evolved in the 1970's. 100% cotton surgical towels were substituted for the huckaback towels; pre-printed chemical indicator sheets replaced the St. Andrews' cross pattern of indicator tape; muslin, and eventually non-woven surgical wrap material replaced the metal casket.