This article from the American Chronicle by Genae-Valecia Hinesman lists and details several signs that parents should watch out for, as they may indicate problems in your child's life. Many of these signals are also applicable for inhalant abuse, but this is a great article to read for any parent.
1. Erratic Behavior
"As young people carve out their own individuality separate from that of their parents´, and seek an answer to the proverbial question, "Who AM I?" they could clash more frequently with those around them. They may be happy one minute and sullen the next. Even this is normal. However, if your child starts reacting violently, either at home or at school, clearly something is seriously wrong."
2. Loss of Coordination, Glazed Eyes, Slurred Speech
"Without question, only two things can explain these symptoms. The first is that the person in question has suffered a stroke or a seizure. The second is that this person is inebriated. Both situations require immediate action. If your child is intoxicated, your first duty is to keep them from leaving the house until sober, for their own safety and the safety of others.
Once they are coherent, find out what they were taking and where they obtained it. If they were found unconscious, and taken to a hospital, medical testing will be able to provide a toxicology report. Encourage them to seek help, if addicted, and at least undergo counseling to learn how to avoid future dependency. Help in any way you can, but let them know that they must want to help themselves, in order to successfully change for the better."
3. Persistant Sadness and Withdrawel from Others
"Any child showing these signs for more than two weeks without interruption is clearly depressed. A change in eating habits and/or grooming has probably also been noticed. If so, something, or a combination of things, has triggered these changes. Your job is to find out what."
4. Honor Student to Dropout
"If your consistently top-notch student suddenly loses interest in school with grades in two or more classes plummeting, take heed! Straight A´s simply don´t turn into D´s overnight. Sit down with him or her and find out what´s happening in your child´s life.
Whatever it happens to be, let him or her know that you´re willing not only to help, but to listen as well. Refuse to accept "Leave me alone!" or "Nothing!" as acceptable answers. If they won´t talk to you, find another trusted adult with whom they will talk. Seek professional help if they need it."
5. Drastic Social Changes
"Friends and companions can and sometimes should, change a bit by the time your child leaves high school. Nevertheless, if your child´s associates suddenly are vastly different in negative ways from those they used to spend time with, this is usually a very bad sign. It´s even more telling if they now avoid or shun their old friends for no readily apparent reason."
6. Finding Unusual Possessions
"Discovering drugs, whether prescription, over-the-counter, or illegal narcotics that you had no idea that your child was using calls for immediate address. The same can be said for condoms, birth control devices, cigarettes, alcohol, and drug paraphernalia of any kind.
Recently, even glue, industrial products, and cleaning supplies have been used as inhalants (known among teens as "huffing") by kids seeking to get "high"-- often with fatal results. Finding these in your child´s room, pockets, or belongings is just as serious as finding a weapon. More than a red flag, this is a screaming siren!"
7. Legal Troubles
"Finally, if your child has been arrested at least once, this is clear indication that the situation is rapidly careening beyond the scope of your reach. By the time law enforcement becomes involved two or more times, your child has become society´s problem and the courts will soon decide his or her future.
Repeated run-ins with legal authorities can never be overlooked as "just a phase". There may still be hope, but only if drastic measures are taken and your child still cares enough to save himself or herself. Only so many chances are given to legal offenders. Don´t let time run out. Intervene while you still can."
These are all excellent points and can be of help to parents who ask, "is my kid abusing inhalants?" The warning signs are often subtle, but they are there.