They can be used very effectively if the operator is familiar with the instrument and aware of their shortcomings. Because of their high sensitivity the investigator could easily misinterpret the results and could for example believe he is following an accelerant trail when in fact the investigator is simply following a trail where a synthetic carpet has become more severely burnt. Sniffers do not respond to the quantity of accelerant present in the debris but to the quantity of accelerant present in the headspace above the debris. Therefore the debris needs to be disturbed before the sniffer probe is inserted amongst the debris. A large area of the fire scene can be scanned in a relatively short time by using techniques such as continuously lifting the debris with a shovel and inserting the sniffer probe under the shovel blade and noting the detector's response.
Sniffers are invaluable when tracing the source of a gas leak.
Sniffer dogs Sniffer dogs are used for the detection of drugs, explosives, corpse location, termites, contraband food and for tracking purposes. Dogs have a sense of smell which is much more sensitive than the human sense of smell. They also have much greater discriminatory powers and can therefore respond much more quickly to target scents. Their physical abilities and their desire to please their handlers enable dogs to thoroughly scan a large area at a fire scene in a relatively short time. Their discriminatory powers are learnt through training.