They also wanted to show solidarity with engineers from Local 39, who are on strike.
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Those workers maintain the hospital facilities and medical equipment.
Officials say talks for a new contract began back in June.
The union refused Kaiser's proposed deal.
They've been in mediation ever since.
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"We are looking for fair and comfortable wages compared to other facilities and Kaiser does not want to meet those," said business representative Jennifer Osborn.
Outside Fresno, tens of thousands of other Kaiser employees have been demonstrating across California and Oregon.
In a statement, Kaiser said in part, "We are offering a reasonable wage increase, and no takeaways, but the union is demanding much more."