The alarm is sounding in the UK’s first drug consumption room.

A man in his 30s has overdosed in the “using space” – a room in the Glasgow facility where nurses supervise injections in eight booths.

He had only arrived at The Thistle minutes earlier, animated about being searched by police on the Gallowgate.

Staff rush to help, bringing him from his seat to a crash mat on the floor.

Our film crew is ushered out of the area while an ambulance is called and staff work to save his life.

Eddie Kearney, a harm reduction worker, tells us that the man had already taken drugs three times that day.

“He’s using a ‘snowball’, he’s using heroin and cocaine,” he explains.

“He’s been in there two minutes and he’s on the floor.”

We are filming in the centre after being granted two days of exclusive access to the pioneering and controversial consumption room.

Less than an hour later, the alarm sounds again, for another man in his 30s.

He had been led to reception by workers from a charity, then made his way to the booths to inject heroin.

Lynn Macdonald, the service manager, tells us it is another medical emergency.

“The first four weeks, there were no medical emergencies, and then this week we’ve had five.

“It could be a batch of drug that is problematic. People are noticing a difference in the heroin when they making it up, saying they are noticing a green tinge to it.”

More paramedics are on their way, she says.

Both men are brought round using the overdose reversal drug Naloxone, before being seen by paramedics. The second is taken to hospital.

Lynn Macdonald later told us: “I am absolutely convinced that had we not been present during the overdoses we’ve seen within the Thistle, then people would not have survived.”

In the 12 weeks since The Thistle opened in the east end of Glasgow, there have been 16 such overdose incidents.

A total of 180 people have visited the unit and more than 1,200 injections of street-bought heroin and cocaine have been supervised.

A total of 27 people have been referred to other services, including housing, by staff.

The service, which follows similar programmes in 18 other countries, seeks to reduce drug-related harm in a hardcore population of injecting users in one of the most deprived communities in Glasgow.

It is hoped that by providing a safer space it will allow medical staff to prevent overdose deaths, reduce blood-borne viruses and clean-up a local area that, historically, has had a major issue with discarded needles and drug debris.

David Clark has been using drugs for 26 years and has spent long periods of his life on the streets.

He allowed BBC Scotland to follow his progress over a three-month period as he attempted to move on from a city centre hostel and stop using heroin and cocaine.

The 47-year-old told Disclosure he used The Thistle service to inject cocaine in February.

From there, staff referred him to new supported accommodation. At the time of his interview, he had been abstinent for two weeks.

He said: “When I went [to the consumption room], it wasn’t what I expected.

“I thought you would go in, do what you’re doing and out. But it’s not like that.

“The members of staff in there supported me and helped me get to where I’m at now.

“It’s helped me massively. I feel better in myself.”

During our visit in early March, we met James – not his real name – who has been injecting drugs for several years. Now in his mid-20s, he was among the first to attend The Thistle.

He says the facility is “brilliant”.

“It’s a lot safer. I was going to car parks, the side of the railway tracks, forests – anywhere I could feel safe enough to do it without getting caught.”

He admitted his drug use in public was dangerous. “Especially on my own, as well. I have OD’d umpteen times.”

The centre remains controversial in the nearby community of Calton.

During the consultation meetings which were held before the project was given the go-ahead, locals had expressed concerns about the area becoming a drug tolerance zone and fears that it would encourage increased drug dealing in the streets.

Linda Watson, one of the most vocal residents, said the centre was already attracting more people to the area to use drugs.

She took Disclosure on a tour of Calton’s known using spots and said there was evidence of freshly discarded needles.

Linda also expressed anger at a lack of investment in the area.

“When we were going to the meetings at first, the drug workers were: ‘We are providing a facility for your community, this will make your community better’.

“But it’s not for people who live in our community. It’s for people who come into our community to buy the drugs, take the drugs and leave all this stuff lying around.

“Why are they not helping us for this not to have happened in the first place? Why have we just got to accept that this is what this place is going to be like all the time?

“Do we not deserve more than that?”

Dr Saket Priyardarshi, associate medical director of drug services at NHS Greater Glasgow and Clyde, said the drug consumption room was not just there to address the health needs of the people using the service.

“It will also improve the social environment for communities, residents, businesses and visitors to these areas,” he said.

“The Thistle will hopefully reduce the drug-related death rates for the population that it serves. But that is a relatively small population compared with Scotland as a whole.

“Its contribution to the national drug death figures won’t be very significant. We have to be honest about that.”

Dr Priyadarshi said much of the anger emanating from the community related to a lack of resources for other services in the area.

“Sometimes I worry that the focus on residential rehab or drug consumption rooms, a focus on debates and discussions about this, takes our eyes off the bigger picture,” he added.

“What are the key drivers here? The key drivers are communities who experience high levels of deprivation and inequality are the ones that experience the highest rates of drug-related deaths and drug-related harms.”

The consumption room was first proposed in 2017 as a response to an HIV outbreak among Glasgow’s injecting drug users, the worst seen in the UK for 30 years.

Health authorities had hoped that offering a sterile place for users to inject would reduce the risk of blood-borne viruses.

However, critics of the scheme said more money should be provided to other recovery services.

Then-Lord Advocate James Wolffe rejected the proposals, which were also turned down by the UK Home Office.

The plan was resurrected in 2021 when the Scottish government announced its national mission to reduce the country’s record drug death totals.

After changes to prosecution policy, which allowed users to bring drugs to the centre without fear of being charged, the centre was approved in September 2023.

It will cost £2.3m per year to run, with funds being provided by the Scottish government over a three-year pilot period.

The government says it is part of a range of measures being introduced to tackle drug deaths in Scotland, which has the highest recorded death rate in Europe.

A final report on the overall impact of the unit is due after the end of the pilot period in 2028.

• Additional reporting by Kevin Anderson and Katie McEvinney