Excessive locks on both interior and exterior doors
Floor fan mounted to a ceiling to distribute production off-gas.
Red phosphorous staining on toilets , sinks, bath and/or showers.
Evidence of methamphetamine production.
Graffiti on walls, floors and ceilings is common in meth production interiors.
Most clandestine drug lab houses are not this obvious.
Alone, these activities or clandestine drug lab signs may not mean that illegal drug lab activity is occurring. However, some or several of them happening together may indicate a problem. Reliable test kits for meth labs are available.