A telltale sign of a meth lab is a powerful chemical smell. The odor of an active meth lab can be like: Paint thinner or varnish smell; Fuel smell; Ether or a "hospital smell" Sour or vinegary smell; Ammonia-like smell (like the smell of window cleaner, fertilizers or even cat urine) Equipment. Meth labs are usually equipped with items such as: More @Wikipedia
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