Litmus strips for measurement of acidity. (Bigstock)

Before their latest discovery, staff members at the Aarows club in Sydney knew the lube dispensers inside had been tampered with in the past.

It’s why they fitted them with security alarms, the BBC reported, to protect patrons seeking out “three levels of adult adventure” at the “gay and bi social club.”

“Our efforts to satisfy the safety and security needs of our clientele since 1990 has created a venue like no other,” its website reads. “Aarows has now long been established as Sydney’s premier health, recreation & social centre where safe sex is permitted regardless of gender.”

The club levels are pocked with rooms for cinema, socializing, yoga, massages and voyeurism. Photos show bar lounges and sex swings, saunas and showers.

And in one of those rooms last weekend, authorities say a 62-year-old man did something sinister.

He lifted the lid of the previously secured lube dispensers and allegedly swapped out the substance inside for hydrochloric acid, a colorless, watery, highly corrosive liquid.

When it touches the skin, hydrochloric acid can cause severe burns and scarring.

The man, who was not named in local media reports, has been charged with several offenses, including malicious damage and administering poison with the intent to cause injury, distress or pain, Australian news outlet ABC reported.

Aarows staff told 7 News Sydney that the man is a regular at the club and a close friend of the owner. Security apprehended the man when he tripped the lube-dispenser alarm, and he was arrested by local authorities.

He was granted bail and is scheduled to appear in court next month, according to ABC.

There have been no reported injuries, 7 News reported. A police spokesman told the Daily Telegraph in Australia that detectives are still establishing a motive but that there was “no indication of hate motivation to date.”

Aarows declined to comment, according to CNN.

Aarows was in the news last year when security footage was released showing a patron being gunned down in the parking garage as he exited the club. He was shot four times, the Telegraph reported, which ruptured his kidney and lacerated his liver. The video shows the man, Michael Rooke, then 52, running through the garage and stumbling toward a door leading back to the club.