Lighthouse Apex Particle Counters compatibility with Vaporized Hydrogen Peroxide (VHP)

Lighthouse Apex Particle Counters compatibility with Vaporized Hydrogen Peroxide (VHP) Medium Image

What is Vaporized Hydrogen Peroxide (VHP)?

VHP is a vapor from hydrogen peroxide H2O2. VHP is produced from a solution of liquid H2O2 and water, by generators specifically designed for the purpose. These generators initially dehumidify the ambient air, then produce VHP by passing aqueous hydrogen peroxide over a vaporizer, and circulate the vapor at a programmed concentration in the air. VHP systems can be used to decontaminate facilities, isolators or small enclosures and pharmaceutical companies generally use VHP in between batches. 

VHP oxidation effects

VHP is a strong oxidizer as it will have a chemical reaction with most materials it is in contact with.

Some grades of stainless steel have been shown to oxidize with H2O2 turning it a light brownish color, the same can be seen with aluminum air sampler heads that turn a greenish color. Therefore material compatibility is very important especially when bringing equipment into a cleanroom.

How can VHP effect a Particle Counter?

As VHP disperses very effectively as a vapor this vapor can get almost everywhere as it was designed to do just that as it deposits on surfaces. At Lighthouse Worldwide Solutions we have tested and designed our particle counters to be VHP resistant externally and internally. Our Apex range come as standard with VHP resistance and a 3 year warranty based on a non-condensing VHP process.

On the outside - Particle Counter Enclosure

Apex Z portable particle counter has a polycarbonate sealed enclosure which was designed specifically to meet the pharmaceutical industry requirements on enclosure wipe down. Making it very durable for cleanroom wipe downs and VHP exposure. The design of the ApexZ enables an easy wipe down with a sealed enclosure and sealed communication ports and power outlets. Without any open crevaces where particles and contamination can build up users can be assured the ApexZ is one of the cleanest particle counters on the market.

On the inside -Particle Counter

With the high grade sealing technology used in Lighthouse Particle Counter designs the probability of VHP finding its way into the inner workings of our particle counters is extremely low. VHP will eventually corrode many surfaces it touches and our seals can be tested and replaced easily during routine service of the instruments. Protecting the insides of a particle counter is very important and needs a lot of consideration in the design. Circuit boards and other sensitive electronics are all susceptible to corrosion. Luckily the Apex range of particle counters have been designed with that in mind and are still the latest generation on the market with this added protection designed into the structure preventing any ingress inside the main enclosure.

The Apex Flow Path

The flow path is the physical path a sample of air would pass through the particle counter sensor as particles in the sample make their way through the laser and optics to be counted and finally exhausted from the sensor. Although there is no FDA or GMP requirement to run a particle counter through a VHP cycle some customer SOP’s require all processes to be fully decontaminated unnecessary as it is the directive still exists and Lighthouse Worldwide Solutions when designing the next generation particle counters made sure that the sensor would not be compromised and data integrity would be intact. Service reports on sensors used in the field which have VHP run through the flow path all have indicated no significant issues and calibration as found data as remained positive and no out of tolerances were observed as long as there has been no VHP condensing and the VHP process has been validated thoroughly by the VHP vendor.

 

Testing Summary and Overview for Chemical Compatibility and exposure H2O2.

The ApexZ which cover portable monitoring requirements in cleanrooms are made up of a polycarbonate enclosure material have other enclosure materials which were all submerged in the following cleaning solutions;

  • Sodium Hypochlorite (Bleach) 8.25%
  • Isopropyl Alcohol 70%
  • Hydrogen Peroxide 35%
  • Spore Klenz (from Steris) 1% H2O2 and 0.08% peroxyacetic acid

The tests were conducted over a 1 week period where the outer body sample materials of the ApexZ were fully submerged in each solution. These tests were accelerated tests to keep the materials in contact with the chemicals for 1 week. However in the real world the instrument would receive a wipe down for disinfection control based on the user guidelines which could be a couple of times a day or week depending on usage.

Each day each sample material was visually inspected and the thickness of each material was checked against the starting thickness. Over the week the thickness of material did not have any significant impact and there was no discoloration observed on the material or any signs of degradation. Below are the summaries of testing completed on the enclosure parts of the ApexZ.

Polycarbonate Enclosure (the body of the ApexZ)

 
Bleach 8.25% Sodium Hypochlorite
Starting Thickness: 0.112
After 7 days: 0.115
% Deviation: %2.6
 
Hydrogen Peroxide 35%
Starting Thickness: 0.113
After 7 days: 0.113
% Deviation: %0
 
Isopropanol 70%
Starting Thickness: 0.122
After 7 days: 0.124
% Deviation: %1.6
 
Spor-Klenz® Ready-to-use
Starting Thickness: 0.113
After 7 days: 0.116
% Deviation: %2.6
 
Thermoplastic Olefin(Covers power jack, I/O cover and sample inlet)
 
Bleach 8.25% Sodium Hypochlorite
Starting Thickness: 0.067
After 7 days: 0.066
% Deviation: %1.5
 
Hydrogen Peroxide 35%
Starting Thickness: 0.067
After 7 days: 0.066
% Deviation: %1.5
 
Isopropanol 70%
Starting Thickness: 0.066
After 7 days: 0.065
% Deviation: %1.5
 
Spor-Klenz® Ready-to-use
Starting Thickness: 0.067
After 7 days: 0.067
% Deviation: %0
 
Steralloy (ApexZ handle)
 
Bleach 8.25% Sodium Hypochlorite
Starting Thickness: 1.028
After 7 days: 1.026
% Deviation: %0.2
 
Hydrogen Peroxide 35%
Starting Thickness: 1.027
After 7 days: 1.022
% Deviation: %0.5
 
Isopropanol 70%
Starting Thickness: 1.032
After 7 days: 1.032
% Deviation: %0
 
Spor-Klenz® Ready-to-use
Starting Thickness: 1.028
After 7 days: 1.023
% Deviation: %0.5
 

* Test criteria for each material was set at a deviation of 3%. ApexZ handle was wiped down with isopropanol every day and showed no signs of swelling or discoloration during the week of wipe down testing

Conclusions

The ApexZ enclosure materials and flow path have all been tested with cleaning solutions and the flow path has been exposed to VHP. The tests conducted on the enclosure verify that the materials are not affected by any oxidation or swelling. With its light and durable enclosure with tight sealing the ApexZ is very well adapted for pharmaceutical cleanroom operations and sterile wipe downs using the most common cleaning solutions found in cleanrooms.

For VHP exposure because of the unknown nature of the VHP process and environment we recommend caution when running VHP through a particle counter. Although the sensor can resists the VHP in some cases when this vapor condenses it can contaminate the sensor leading to bad data and calibration failure. Therefore unless the process has been fully validated by the customer we would advise the end user to cap the sample inlet and turn off the internal pump or vacuum when using a remote particle counter. There is no GMP or FDA requirement to use a particle counter during cleaning cycles. With the risk of condensing and the high probability of bad data and introduction of contamination into the sensor not monitoring during cleaning cycles is a prudent choice and one that will be a less expensive option and keep your particle counter from needing costly repairs.

Jason Kelly; VP of Services Lighthouse Worldwide Solutions
Mar 19, 2021