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Middlesex-London Health Unit

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Cannabis Grow Operations

Cannabis grow operations, also known as marijuana grow operations (MGOs) or grow ops, involve houses or buildings that have been changed to grow large amounts of cannabis. The cannabis produced is then sold illegally by criminal groups. Cannabis grow operations typically result in electrical, structural, fire, and health hazards within the building they are located. The size and scope of these hazards can change from one grow operation to another.

Note: As of October 17, 2018, the Cannabis Act permits adults to cultivate up to 4 cannabis plants per household (not per person). There are recommended safety and security measures for growing cannabis plants. As well, know the facts about the Environmental Health Risks of Personal Cannabis Cultivation (PDF 203KB).

How to Identify a Cannabis Grow Operation

Cannabis grow operations typically occur in residential homes, but can be found in commercial buildings. People that run these operations often illegally tap into hydro sources so that they have electricity to power lights, fans, ventilation systems, heaters, and automated watering devices. They may tamper with the electrical meter or electrical wires outside of the building. Often, a hole to access the electrical supply might be drilled or hammered through the building’s foundation, weakening the structural support of the building. Electrical tie-ins could also occur in roof soffit locations in older homes where wires are above ground.

Houses operating as cannabis grow operations may or may not be lived in. You may notice irregular or unusual activity around the property. You may also notice the home and lawn are untidy, lights that are controlled by timers, or windows that are covered to stop public interest. Conditions within the home will be humid and warm. Depending on the length of time the grow operation has been running, the walls and other surfaces that can take in moisture may be covered in mould.

Reporting a Cannabis Grow Operation

If you wish to report a cannabis grow operation to the London Police Service, please call:

  • 519-661-5670

To provide an anonymous tip about a cannabis grow operation to the London-Elgin-Middlesex Crime Stoppers, please call:

  • 1-800-222-TIPS (8477)

What steps are taken to restore a Cannabis Grow Operation within the City of London?

After the City Clerk receives a report from the London Police Service about a house or building that was found operating as a cannabis grow operation, the City of London’s municipal by-law enforcement division, Property Standards, will be notified. When the house is in the recovery stage, the municipal by-law enforcement division will decide the steps that are needed to restore the house.

To make a former cannabis grow operation house safe, all health hazards and possible health hazards must be fixed.  At the request of the City of London, the Middlesex-London Health Unit’s Environmental Health Team created a document to guide Certified Industrial Hygienists on the proper steps to take to restore former cannabis grow operations. These steps involve a thorough visual inspection for moulds and other possible hazards, as well as air sample testing for fungus and moulds. Engineering assessments are also done to decide whether or not structural or electrical hazards exist. 

Buying a Former Cannabis Grow Operation Home

Cannabis grow operation houses are often on the market for sale either “as is” or “cleared” through the City of London or local municipality. If you are interested in buying a former cannabis grow operation home, make sure that you properly check to see if there are any outstanding or upcoming legal orders on the property. Keep in mind that these buildings can be in the legal process for some time.

It is the responsibility of the Real Estate Agent to tell you that a house was a former cannabis grow operation. You can also check to see if a house in London, Ontario was discovered to be a grow operation. To do this you will need to complete the Grow Op Property Check process through the London Police Service.

The Middlesex-London Health Unit suggests that people who are considering buying a former cannabis grow operation home speak with a Certified Industrial Hygienist if they suspect anything unusual about the home, such as musty odours, visible mould, or moisture damage.

It is important to note that former cannabis grow operation homes can sit for long periods of time after the recovery stage assessment. Therefore, it is impossible to guarantee that no mould has grown after the assessment date.

Date of creation: December 10, 2012
Last modified on: January 19, 2022