Odour control in cannabis grow rooms

Odour control in cannabis grow rooms

If you can keep prevent grow room smells escaping outdoors you significantly increase your chances of finishing your grow safely.  Poor odour control in cannabis grow rooms is one of the main reasons that growers have their crops confiscated. 

Here are some top tips to make sure you never get caught.

Carbon filters

Its one of the most important investments in your grow room, and its so important that many growers always have a spare carbon filter just in case an urgent change is needed.  Carbon filters work by removing the aromatic terpenes and locking them inside the filter. 

One of the generally accepted rules of indoor growing is that a carbon filter is an essential part of your grow room equipment.  Trying to run your carbon filter until it is at the end of its life is false economy, many growers prefer to switch to a new carbon filter long before the old one is finished for maximum safety.  Carbon filters tend to last longer in low humidity.

Ozone generators

These are not regarded as essential as Carbon filters, and not everyone likes them for safety reasons – Ozone can be dangerous.  But for some growers an Ozone generator is a guarantee that even a slight odour that may escape the carbon filter will be safely removed. 

Ozone generators are usually placed in the waste air stream which exits from the carbon filter.  However they do require careful control to get the correct ozone level.  If you produce excessive Ozone in an urban setting it may draw unwanted attention.

Proper seal

Ensure a proper seal between carbon filter, fan and the ducting.  Without air tight seals you can accidentally pull unfiltered air out of your grow room which will be noticed outside. 

Many hydro shops sell basic as well as more expensive professional ducts seals.

Get rid of waste air

Find the best way to get rid of the waste air from your grow room.  Many growers prefer to force it out through a roof chimney.  Other growers will connect the waste air duct to an air brick  in the loft.  Some people simply vent the waste air into the loft space – however that allows heat to build up inside the loft, and in winter that could be a problem. 

A warm roof space may never be noticed in summer, but in winter a warm roof prevents frost and snow and may be a giveaway sign of cannabis growing.  If possible, vent the warm waste air directly outdoors.  And if possible try to vent the air away from people, around the back of the house rather than by the front door. 

In reality many home growers (e.g. those living in apartments) have no other choice but to vent the air back indoors.  Its not ideal, but for many it works well if the filter is replaced regularly and the apartment has plenty of fresh air exchange via an open window.

Compatibility between fan and carbon filter

Ensure compatibility between your fan and carbon filter.  There is no point having an extraction fan which pumps too much waste air through a small carbon filter. 

If the filter cant handle the air volume then you need a bigger carbon filter or smells will escape outdoors.  Websites of the fan/filter companies explain the details 

Low odour strains? 

Some growers feel that certain low odour varieties can be grown with less precautions.  However most growers feel that even a low odour variety will still produce a strong odour in full bloom. 

So don’t rely on the plant genetics, make sure you have carefully planned your grow room to deal with the odours.

Use of a second carbon filter

Some of the larger legal grows vent the waste air into an internal room.  This air is then filtered through a second carbon filter before finally venting outdoors.  For many people this is unnecessary, but its interesting to see how some of the USA legal growers deal with odour issues.

Ona Gel

This gel is often used in USA dispensaries to reduce odour.  It contains natural plant extracts which remove smells and can be used in combination with other odour control methods. 

Ona gel tends to be most popular outside the grow room, often used ‘just in case’ there are any residual cannabis smells around the house.

Harvesting tips 

Some growers feel that the best way to harvest their cannabis is to get inside the tent, zip it back up and start chopping.  Other growers prefer to harvest with the tent door open when they know there will be less people around, perhaps late at night.  

Growing cannabis is easy, and with a few simple precautions it is also safe.  But the safest way to grow cannabis indoors is always to plan your grow to remove the smells.