We are often asked how many sachets you should use in your wardrobes and drawers for moth protection and prevention. Often if you've had an experience with chemical repellents there will be a guide for how square metres of space they will protect - usually these are based on safety guidelines for the particular biocides being used. As guidelines you can see that the efficacy of the product is going to be different in a wardrobe that is so jammed with clothes you have a battle pulling something out compared to a wardrobe where there is space between hangers. Indeed the crammed wardrobe is often a far more attractive breeding ground for moths as they can lie undisturbed getting upto mischief for far longer than a wardrobe where there is some breathing room for your clothes.
I've often recommended a hanging sachet every 4-6 hangers as a guideline and either a large drawer sachet or perhaps a couple of mini sachets per drawer. We do have clients who use considerably more and they often explain that it's because they've had a bad experience where they have lost many thousands of pounds of precious garments and they'd rather be over cautious. As moth damage is excluded on household insurance policies it's a risk you need to manage yourself. You should always consider the value of what you're trying to protect - be it a favourite cashmere jumper or entire wardrobes full of extremely expensive designer clothes. As you are effectively self insuring the risk, you'd be wise to spend more when you have a lot to protect and to prioritise periodic checking of your clothes and fabrics.
We have a number of clients who use Colibri within stately homes - and they are often amongst the best organised in terms of replacing their sachets. While we recommend a periodic check every few months and giving the sachets a good scrunch (the cotton paper which houses the powder which is suffused with essential oils is robust and can be agitated to move the contents around and get those protective essential oils whizzing around your wardrobe). If you're using products like our cedar blocks then these will benefit from periodic sanding to release more of the essential oils held within the wood.
Changing the sachets every 6 months is recommended - but use your nose. While moths have an olfactory system which is far more powerful than humans - if you can still detect the fragrance then they certainly will. I also find that some clients will move from one fragrance (cedar, lavender or lemongrass) to another each time they change their sachets to ensure they are changing the all products on time and this provides a useful visual checklist. The value of checking periodically is to alert yourself to issues - over the years we've had many an unfortunate client who has added a vintage piece of clothing to their wardrobe only to find out they have introduced some unwanted guest (always a wise move to dry clean vintage garments before mixing them in with your other clothing).