I have heard that the smell is of ammonia and sharp chemicals. The police in this state are more than eager to investigate. They'll even check out annonymous reports. I've never heard of the police NOT checking out suspected meth labs.

It can sometimes smell like ammonia (or cat pee, if that is easier for you.) How will it affect you? Well, it might not affect you at all. It could pose a danger in the way of explosions or fires, though. If the chemicals aren't disposed of you could also be exposed to the leftover hazardous materials. If the meth lab leads to meth being sold and increased meth use in the house, it could also hurt your property value. Police are usually very keen to investigate suspected meth labs. If you have notified them and they haven't arrested anyone then chances are they found nothing to support your claim. If you are quite sure that there is a lab and they failed to even check it out then you could ask to speak to their superior or contact your state bureau of investigation.

As far as proof, you may want to consider taking notes as to the dates/times you see vehicles coming to the property (maybe buying?). Tag numbers are also useful. However, never at any time should you risk yourself to get this information.

Usually not at all. Well in my case it makes it that much easier for me to get high... if you know what I mean. Labs come in all shapes and sizes. The lab next door is usually "personal" one man operation in a private home. Usually he or she is cooking up enough for themselves and maybe something to make a little profit on. This is becoming more and more popular as the law cracks down on the materials for making meth. The toxic by products are dumped down the drain and you will not smell much of anything. A small explosion may take place - but if there is a problem it will be a fire no different than say a dropped smoke or bad wiring. Big time cooks tends to like having fronts (store front) rent a large house, blah) Labs and dealers are usually not all in the same place. There will be usually one or two mules (people who carry the drug) that will come and go on a regular basis, maybe a few cooks. The lab itself will appear "normal" low traffic, seeming a "normal" family with the same few people coming by to visit each day. The "mules" will carry out large quantities of the drug and distribute to franchise operators (dealers) who in turn operate far away from the lab. In short you are dealing with criminals. They know what they are doing is illegal therefore they take great pains to not be caught. If you have contacted the police and something really is going on over there most likely the immediate reaction will not be satisfying. Remember the "mules"? along with them there are many others who buy the materials. The laws that limit the sales of OTC drugs used in the making of meth means that many people (usually users) have to go out to many stores to buy one or two packs of Cold Medicine (example). So there are many people involved with the operation. Drug deals or passing on drugs is not always easy to detect, even to the police or hard core drug users. There are many ways to pass on drugs without looking like any drug is being passed. It takes time to piece it all together. Thus calling the police will result in investigation and monitoring the situation - a "sting operation" which can take months sometimes years to complete where they let the lab crank out crank while the police follow individuals and map out the network. The bigger the operation, the longer the investigation before any arrests are made.

meth labs will emit a gas smell, kind of like living next to a permanent gas leak. for the evidence part... report the house annonymously a lot, within a couple weeks you'll see a random car parked out front a lot...love those undercovers :)