Greenhouse Hygiene Practices to Reduce & Contain Pest Outbreaks: #2 Keep Room Clean using Recirculated Air

Environmental Monitor panel
Recirculated air prevents the growth of mold and mildew, commonly introduced by using outside air. Maximize plant growth and minimize pests.

Photo by: Kit Galvin


notes icon Take note

Controlling the room’s humidity and recirculating air minimizes pests and maintains plant health. Less pests equals less pesticide use which reduces worker’s exposures to chemical products.


alert icon Alert

Use of CO2 in the workplace can be a worker health hazard if safety precautions are not in place. High levels of CO2 levels can replace too much oxygen. Typical levels of CO2 that enhance plant growth should not be a risk to worker health. Levels that are a worker health risk are not healthy for plants. It is important to include CO2 in the chemical hazard communication and CO2 exposure prevention plans in your company's safety program.


idea icon Idea...

Recirculating air is beneficial because it keeps the temperature uniform throughout the room, reducing humidity on leaf surfaces. Outdoor air through the ventilation system can introduce pests (spider mites, whiteflies etc) into the room. An environmental monitor informs workers of the current conditions so adjustments to carbon dioxide (CO2) levels, relative humidity, and temperature can be made as needed.


“Mold and mildew common in outdoor air do not grow in the rooms because outdoor air is not used. Worker exposure to products used to remove mold and mildew is reduced. I highly recommend it to other workplaces, but they need to keep in mind that it will require customization which may not be feasible in older or larger operations.”
Greenhouse worker

setup icon Setup & use

  1. Check the temperature, relative humidity, and CO2 levels on the environmental monitor to see if they are appropriate for that room.
  2. Contact designated staff if settings need adjusting before entering the room.
  3. Adjust environmental conditions to meet the room specifications before entering the room.

supplies icon Supplies

  • Environmental monitor
    • Select an environmental monitor base unit and sensors appropriate for your ventilation systems for the greenhouse and/or controlled environment rooms.
    • Consult with an electrician to properly install the environmental monitor.

tips icon Tips

  • Provide training for all workers that may enter the rooms including:
    • Room entry procedures and dos and don’ts
    • Hazard communications for specific chemicals (ie. CO2) used in the room
  • Designate authorized personnel allowed to change room environmental settings
CO2 monitor in greenhouse
CO2 Monitor in greenhouse.

General Nursery and Greenhouse Resources

WorkSafe BC (Canada)

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We hope that you will be inspired you to incorporate solutions into your own training style, develop your own hands-on teaching tools, or discover new practical solutions. We hope that you are inspired to use these solutions in your workplace. Did you try one of the practical solutions or develop a new one? We would appreciate hearing about your ideas and experiences.

Thank you and safe pesticide handling,

Contact your state agency for more information on WPS regulations. The content of this website is for informational purposes only. It may need modification to fit your needs or it may not be appropriate for your workplace. Safe use of these solutions is your responsibility. The University of Washington and the Pacific Northwest Agricultural Safety & Health Center is not responsible for any loss or damage resulting from the use of the information provided on this website.

PNASH Project 2016-2021 (CDC/NIOSH Cooperative Agreement # U54 OH007544)

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