A WorkSafe investigation is underway at a West Australian lithium plant after complaints about an unsafe work environment. 

The investigation into the Kemerton lithium hydroxide facility, about 150 kilometres south of Perth, began in early April following an incident in which staff were exposed to potentially harmful gases.

A handful of workers were taken to hospital as a precaution after they were exposed to toxic gases through a vent. 

The Department of Mines, Industry Regulation and Safety (DMIRS) confirmed the investigation and said it had been visiting the site due to complaints as well as routine checks since at least September 2020.

The facility is majority-owned by US chemical company Albemarle, with the plant simultaneously being operational and under construction.

Albemarle was unwilling to confirm the investigation to the ABC, but said that safety was the company's top priority. 

"Albemarle provides a safe working environment for a workforce that is highly trained in the use of the equipment and behaviours required to maintain safe operations," the company said. 

"We continue to collaborate productively with authorities in the regulation and management of our site."

'Consequences for unsafe workplace'

Concerns about the safety of Albemarle's workplace have been raised by the Australian Manufacturing Workers' Union (AMWU), which described it as a "21st-century facility with a 19th-century workplace safety culture".

Union state secretary Steve McCartney said he wanted the investigation finished as soon as possible. 

"We wanted to make sure that the parent company understood the consequences of having an unsafe workplace, and to make sure that the head contractor that runs the construction has a real plan for safety in the future," he said. 

"We want the outcome from DMIRS, so that we can make sure that this facility is compelled to work to the rules are they committed to working to.

Mr McCartney said previous issues at the workplace included chemical showers not working and aluminium scaffolding being stored next to a corrosive substance. 

The AMWU also said a COVID-19 outbreak at the facility in January was handled with poor communication.

Albemarle exploring expansion

The WorkSafe investigation follows an announcement from Albemarle it was considering a potential expansion of its Kemerton operations.

It includes plans to build a worker accommodation village in Binningup that would house up to 1,000 workers. 

Residents are pushing to ensure the small seaside community sees long-term benefits from the project, expressing concern that a large influx of workers will put further strain on the town.

Binningup Caravan Park owner Jason Rule said the community was uncertain.

"No-one really knows what we're going to end up with at the end of it all, and the effects it's going to have on the lifestyle on the people that live in the town," Mr Rule said.

An expansion is back on the cards as the price index for lithium hydroxide increased more than 400 per cent over the past year.