Spray vapor molecules tinier than micron size

Common particle filters down to the smallest micron cannot prevent pesticide vapours from entering your lungs. That’s because vapours are molecules, far smaller than particles, and that’s why vapours are dangerous.

Common liquids exist in one of three forms, according to Tom Wolf of Agrimetrix in Saskatoon. When frozen it’s solid. When it warms to a certain thaw temperature it becomes liquid. When heated or manipulated by a spray nozzle it goes into its gaseous form, which is a vapour. The individual molecules are airborne. They are no longer part of a larger structure, which is why they can sneak through a particle filter.

“The vapours we get in spraying pesticides are very small. By their definition, they’re smaller than micron sizes. They are molecules, the gaseous phase of a product,” says Wolf.

“Take a product like dicamba or any of the ester formulations. It’s not the chemical itself that’s volatile, it’s the organic solvent that’s typically volatile. You have an organic solvent to dissolve the oily pesticide in an emulsion. If you can smell it wearing your mask, that’s the organic solvent you’re smelling.”

He warns that if you smell anything inside your mask, then the respirator is not working properly. You should never be able to smell the esters. If you do smell them, it’s time to change cartridges or re-adjust the mask.

Wolf says his research team uses a silicon half mask that creates a tight seal around the person’s face.

To test the fit of a respirator mask, his team uses a Bitrex spray that has a very bitter flavour. If the person inside the respirator smells the Bitrex, then it’s back to the fitting room to re-adjust the mask. Wolf is certified as a fit-tester for respirators.

“I always emphasize that a particle filter will not stop vapours from getting into your mask and into your lungs. You need a vapour cartridge for organic vapours. That’s a screw-on cartridge, one for each side. In front of that there’s a particle pre-filter that’s like an N95 filter. You snap that on over the vapour cartridge.

“Sprayer cabs are built with charcoal or carbon vapour filters integrated into the air circulation systems. That’s the same filter material we have in our vapour cartridges. It absorbs the vapours.

“Pesticide labels differ on their respirator requirements. Many labels require a respirator when mixing and loading. Applicators need to check each label to be sure they and their staff take appropriate (personal protective equipment) precautions.”

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