Find the nest route
Watch from a safe distance to see whether insects repeatedly enter one point. Do not seal a wall void while a concealed colony is active unless the control plan accounts for where the insects will go.
Avoid unnecessary disturbance
Vibration, blocking the entrance or spraying from an unsafe position can increase sting risk.
Use the label
If using a domestic product, confirm the label covers wasps/hornets and the exact treatment location. Keep people and pets away as directed.
Professional situations
High nests, wall-void nests, ladder work, heavy traffic areas and known severe sting allergy are sensible reasons to hire help.
Canadian rule: if a pesticide is part of the plan, use only a product registered in Canada and follow the label for the named pest and treatment location. Provincial and municipal restrictions can still apply.