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Two Aerial Disinfection Programmes

by 5m Editor
29 March 2001, at 12:00am

Further to our article highlighting the possibilities of Aerial Disinfection as a method to help reduce the airbourne risk of infectious disease such as foot-and-mouth this article details two different methods that can be used to achieve aerial disinfection. Information provided by DAHS based in their Virkon S systems.

Misting System using Virkon S

A mechanical application of disinfectant at small particle size to reduce dust and airborne pathogens in small to medium sized buildings. In very small areas a knapsack sprayer could be used to generate sufficient mist

A. Prepare a 1:200 dilution of Virkon S to fill your mister
  1. Add 5g of Virkon S to every litre of water.
    (NB: Avoid contact of Virkon S with skin and eyes)
  2. Stir solution until fully dissolved (Virkon S dissolves faster in warm water)
  3. Add solution to mister (e.g. Stihl , Dyna fog etc) or knapsack sprayer
B. Application using a mister
  1. Position misting apparatus where it is capable of treating all the air in the building. In larger rooms it may be necessary to move the mister around the building.
  2. Taking care to avoid startling livestock if present, ensure the entire volume of the building is treated. Pay attention to the eaves of buildings.
  3. To protect at risk animals against foot-and-mouth disease apply at a rate of 1 litre/10 sq.m. of floor space at least twice-a-day.
Thermal Fog Application System using Virkon S

Introduction

The use of thermal fogging is accepted practice for the final stage of full disinfection programmes. This method of disinfectant application can be rapid and does not involve large volumes of liquids in buildings where equipment and litter is already installed.

The drawback of the low volumes that are applied in this way is that there is insufficient penetration of organic matter and porous surfaces for thermal fogging to be effective for primary disinfection, its successful use needs to follow thorough clean out, wash down and spray disinfection.

The disinfectants commonly recommended for thermal fogging are based on formaldehyde and glutaraldehyde, but these chemicals have two major drawbacks:

Problems with the use of aldehydes

1. Toxicity
Health and Safety legislation now requires the monitoring of exposure to these dangerous chemicals. This is both expensive and impractical under farm and industrial conditions.

With formaldehyde excess levels are easily detectable by smell, but with glutaralde hydeoccupational exposure levels of 0.05 parts per million can easily be exceeded without warning.

A recent press release from the Health and Safety Executive states;

"Some disinfectants present greater risk, for example HSE recently described that a review of the evidence about ill health linked to glutaraldehyde concluded there was no safe level at which there was no risk of serious health effects. This chemical, which is widely used on farms has been linked to occupational asthma, eye and throat irritation and may cause allergic dermatitis."

2. Time
Due to the high levels of toxic vapour that persist after fogging the entry and restocking of buildings is delayed for up to 48 hours.

Advantages of the Virkon Thermal Fog System

With the development of safer disinfection systems such as Virkon S, aldehydes can be replaced for spray disinfection, and now with the Virkon S thermal fog system Virkon can be used for the complete disinfection programme.

The Virkon S thermal fog system consists of: Virkon S the supreme broad spectrum virucidal disinfectant plus Virkon S fog enhancer. The combination of these two products in an aqueous solution when used through commonly available thermal foggers creates a dense fog which gives a level of disinfection suitable for the final stage in a full biosecurity programme.

The Virkon S plus fog enhancer system has two important advantages:-

1. Safety
The Virkon plus fog enhancer system used as directed creates no toxic hazard to the operators.

2. Speed
Because it is so safe operators can enter the building as soon as the fog has dispersed.

Trials on commercial units have demonstrated the compatibility with existing thermal fogging equipment

Comparative trials have demonstrated reductions in the level of bacterial contamination similar to that for formalin and better than glutaraldehyde / quaternary ammonium compound (QAC) mixtures.

Trial results

1) UK Commercial Broiler Farm

4 houses each of 7500 sq. ft floor area (700m2)

Total bacteria counts /cm2 (average counts by swabbing)

System Before After Reduction
Virkon S 19079 1374 92.7%
Formalin 23270 1555 93.3%
Glutaraldehyde / QAC 22800 13688 40%

Use of products at commercially used rates:

Product Usage rate
Virkon S 2kg / 1000m2
Formalin 15 litres / 1000m2
Glutaraldehyde / QAC 500ml / 1000m2

Application followed clean out, washdown and spray disinfection.

2) UK commercial broiler farm

3 houses of 7450 sq. ft floor area (700 m2)

Total bacteria counts /cm2 (average by swabbing).

System Site Before After Reduction.
Virkon S drinker 150000 13188 91.2%
wall 12813 2282 82.2%
roof 1500 167 88.9%
posts 6880 566 91.7%
Formalin drinkers 343750 48000 86.0%
wall 3063 1211 60.0%
roof 3750 44 98.8%
posts 2500 25 99.0%
Glutaraldehyde / QAC drinkers 118750 18458 84.5%
wall 6563 2188 66.7%
roof 4187 910 78.2%
posts 1860 541 70.9%

Use of products at manufacturers recommended rates

Product Recommended usage
Virkon S 2 kg / 1000m2
Formalin (38%) 25 litres / 1000m2
Glutaraldehyde / QAC 1 litre / 1000m2

Application followed clean out, soak and wash down, and spray disinfection according to normal commercial practice.

Virkon S Fog Enhancer Precautions

No special precautions are required for handling Virkon S Fog Enhancer. However, as with all chemicals it is advisable to wear gloves and eye protection when handling the concentrate. If it is necessary to enter the building during fogging, wear suitable respiratory protection (e.g. Arco filtermax face mask and A2 filter)

Emergency and First Aid Procedures

Eye contact: Thoroughly irrigate with water or eye wash for 10 minutes. Seek medical advice.
Skin contact: Remove contaminated clothing and wash with water
Ingestion: Do not induce vomiting. Wash out mouth, drink 300 ml of water. Seek medical advice.
Inhalation: Remove from exposure and seek medical advice if adverse effects occur.

Further Information

Information on Aerial Disinfection can be found on this web site. Alternatively visit the DAHS web site

2001
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