But two months later his life was in tatters after he lost his job due to getting seizures in the workplace, fits that also led to his being banned from driving until he had been seizure-free for 12 months, because medical experts could not be sure they would not happen again.
"I wasn't a heavy user of K2, just a couple of nights a week to help me relax after work, and I thought that because it was legal it must be safe. But boy was I wrong. It's caused me major problems."
About two months after starting smoking K2 he had had a seizure at work, the morning after having a toke at home.
"It was the first time I ever had anything like that happen to me. I just completely blacked out and can't remember anything about it, but I was fitting, and my arms and legs were jerking about and I was foaming at the mouth," he said.
"All I can remember is waking up in the ambulance on the way to hospital wondering what the hell was going on, but I didn't link it to K2 at that stage."
He was taken to hospital, but doctors were unable to find out what was wrong. His workplace stuck by him, but said he would not be able to drive any of its vehicles. Then a short time later he had another seizure at work and he had to be let go because of his inability to drive and concerns over workplace safety.
Mr Van Harlingen admits he didn't read the instructions on the K2 closely, but assumed it would be like cannabis, given that it was marketed as synthetic cannabis. "But it was different from cannabis and much worse. There was something odd about the feeling it gave."
While the doctors were struggling to find out what was wrong with him, the seizures ceased within days of quitting K2 and now, three months later, he has not had another.
"Now I'm on a sickness benefit and nobody will employ me because I can't drive for 12 months and because I've had seizures at work. It's messed my life up big time," Mr Van Harlingen said.
A Psychoactive Substances Bill has been tabled in Parliament by Associate Health Minister Peter Dunne and is expected to pass by August 1. The bill will restrict the importation, manufacture, and supply of psychoactive substances and only allow the sale of psychoactive substances that can meet safety and manufacturing requirements.
But Mr Van Harlingen said August was too long to wait: "It needs to happen now. This stuff is just too dangerous."