What type of system do handlers use when mixing pesticides packaged in water-soluble packets?

Handlers use a closed mixing system when mixing pesticides packaged in water-soluble packets to minimize exposure to the chemicals. This type of system is designed to contain pesticides within a sealed environment during the mixing process, preventing any escape of chemicals into the air or onto the handler. Closed systems often include features such as spill containment, automatic mixing, and direct delivery methods that reduce the likelihood of spills or drips.

Using a closed mixing system is particularly important for water-soluble packets because of the concentrated nature of the pesticides within these packets. This approach enhances safety by ensuring that handlers are not directly exposed to potentially harmful substances during the mixing process.

The other options relate to different aspects of safety or equipment in pest control but do not specifically address the needs for handling the unique properties of water-soluble packets in terms of mixing. Passive rinsing systems, personal protective equipment, and non-engineering control devices do not provide the same level of containment and safety that a closed mixing system offers, making it the correct choice for this scenario.