After the meth manufacture process has finished, most of the immediate hazards decrease. However, some residual contamination created from repeated "cooks" can remain long after all production has stopped causing health problems. Harmful chemicals can be volatilized or aerosolized during the cooking process and deposited on surfaces and materials. Contaminants in air are absorbed into porous materials including drapes, carpets, furniture, rugs and other surfaces and may also contaminate the heating system of the residence. Spills are common in meth labs and my impact appliances, walls, floors and other nonporous surfaces. Clandestine meth production also include hazardous chemicals which may be dumped down the toilets, drains and/or sinks and leave contamination in the waste water system. 

To know if your home is contaminated with residue from smoking meth or to check for meth residue remaining from a clandestine drug lab, you need to perform testing.  It's that simple.