I am going to address this from a place of addiction. I am a recovering alcoholic and a smoker. Addiction to a substance is a terrible thing. There are people who can use and abuse substances and yes, they are addicted but do not have that ADDICT personality. It sounds like he does. Lying and hiding goes along with this. The consequences of my drinking were obvious and caused pain for my family. The consequences of smoking seem far away so its easier to justify. He lies because of shame, and hides because he fears disappointing you. It makes sense because he is, right? And for so long because of that he got used to hiding things and lying so that now, even though you told him to just vape he is in the habit of being dishonest about it. He sounds like a true addict even though its not drugs or alcohol, its the same thing. My mom smoked for years and then one day she stopped and had no issues. I have stopped and started a thousand times. My fear of relapsing on alcohol is what makes it hard to quit smoking. An excuse Id like to get over. When you first got together was he a smoker or vaper? If so he may look at it as you knew what you signed up for and resent being asked to change. Maybe couples counseling could help. I think as far as addressing it with him it would be a good idea to gather your thoughts and take a deep breath and calmly tell him that yes, he can vape-outside. But no, he can not lie about it or hide it. Tell him that lying about it is the crux of the issue. Decide what consequences there might be if he lies about it. Tell him that you want him to not feel he has to be dishonest about it. He is a grown man who is choosing to do this, so he should be grown enough to just do it without the lying. Can you live with him and stay with him if he chooses to vape or smoke? You may never change him and you really need to assess whether you can live long term with his decision.