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Fogging

11/17/2021 Newsletter:

Treatment Terminology by Jeff Waggoner, ACE

Fogging is NOT Fumigation.  In fact, not even close.  There are also different fogging methods that will vary greatly in efficacy.

Let’s discuss, shall we?  If you have a flour beetle problem and your PCO is using a thermal fogger, then you might not like the results, and one might tend to think that fogging doesn’t work very well.  On the contrary, fogging works very well.  If you use a compressed gas mixture or several mechanical foggers placed in strategic locations to improve your droplet dispersion, then you may have a different opinion on fogging.  But it’s still not a fumigation.

Scale:  Fogging applications are typically performed at a 15-micron size.  At that size, you can still see the droplets since when suspended they scatter enough light to see the “fog”.  Now, Vapona DDVP which when fully vaporized ends up around 5 microns in size.  Even when fogged, Vapona cannot be seen.  Thus why, vapor is not apparent in the air after a Vapona fogging.  15 microns about 1/4th the width of a human hair which is 60 microns at the small end of the hair spectrum.  A fumigant molecule is smaller yet and is also invisible to the naked eye.

How in the world can we be effective at killing insects with such a small dose?  Several factors apply.

  • Proper Sanitation
  • Location of Infestation
  • Insect Species (crawling, flying, reclusive or buried in product, equipment, etc.)
  • Timing of Application(s)
  • Delivery Method (type of fogger)
  • Delivery Points (sufficient dispersal sites).

1 oz. of product per 1,000 cubic feet is a typical dosage rate for diluted chemicals labeled for space applications.  That’s not a lot of chemical.  You need to ensure facilities properly prepare for a fogging by performing exceptional sanitation before the application.    A fumigant can penetrate through equipment, conduit, some packaging materials, or dense products to reach the epicenter of a hidden infestation.

You can also increase effectiveness of a fogging by pre-treating surfaces.  All cracks and crevices can be sprayed with an approved insecticide prior to fogging.  Especially around known problematic areas.  You cannot spray equipment and certainly not food contact surfaces with your pre-treatment.  Note:  Always read how to protect food contact surfaces when doing a fogging.  A fogging is essentially a “space spray”.  It will state cover, cover, and wash or do not apply if present, etc.  You will also want to watch for any open product.  It should be covered or removed typically.  FSS, Inc. uses a preparation document we call a FogPro.  This will help ensure safety and success.

So, what’s the difference?  Fumigation is a gaseous space treatment.  A fumigant is a liquid under pressure or a solid that goes through a chemical change and becomes a gas.  Let’s use Sulfuryl Fluoride for example.  It’s a gas at normal atmospheric pressure and is inhaled by an insect.  A chemical fogging agent is delivered to the insect as a contact insecticide.  Gas is molecule size and fogging is micron size.  You must contain a fumigant in high enough concentrations over a period of time so the insect or rodent can inhale it until it dies.  This can happen in several hours to several days depending on the conditions.  A fogging is usually completed in a few hours since all the chemical will “fall out” by that time.  Please note that Vapona may require up to 24 hours for ventilation before returning to the area.

When you are considering control options it helps to know the terminology, limitations, and advantages of each type of application.  Sometimes decisions are time, quality, or budget oriented.  Learn more and discuss your options with a qualified FSS, Inc. representative today!

Fun Fact:  The Sulfuryl Fluoride molecule measures roughly 145pm (picometers) in diameter (145 trillionth of a meter).  In other words, the diameter of a 5-micron particle is equal to 35,000 SF molecules all lined up in a row.