Handlers who properly mix pesticides packaged in water-soluble packets are considered to be using?

Handlers who properly mix pesticides packaged in water-soluble packets are indeed considered to be using a closed mixing system. This type of system is designed to minimize the exposure of handlers to hazardous substances by containing the pesticides within a sealed environment during the mixing process. Water-soluble packets dissolve completely in water, thereby allowing the handler to avoid direct contact with the concentrated pesticide.

In a closed mixing system, the risk of spills, splashes, and airborne exposure is significantly reduced, promoting safety and regulatory compliance. This method aligns with safety protocols and best practices, especially in the handling of chemicals that could pose health risks. As for the other options, open mixing systems expose handlers directly to the chemical, while semi-closed systems may still allow some level of exposure. Manual mixing does not include the protective measures that closed systems provide, making them less favorable from a safety standpoint.