Trade unionist lawmaker Lam Chun-sing says a recent survey shows employers and their staff differ over whether enough measures have been taken to avoid heat stress.

The Federation of Hong Kong and Kowloon Labour Unions and the Hong Kong Workers' Health Centre interviewed over 100 construction and cleaning workers and 36 employers. It found the majority of employers felt the updated heat guidelines were difficult to understand, with both workers and bosses unsure of which workload category that staff were in.

Lam also said some employers felt that simply providing a portable fan was enough.

"The reason is that, for example, some of the outdoor workers.... their employer provided a portable fan and in the first hour it's okay. It can reduce the rest time. But in the second hour or later, the portable fan does not work. No electricity," Lam said

Lam said 40 percent of the employees surveyed said that their employer did not mention or introduce the guidelines to them. And 50 percent of employees said, even under the amber warning signal, the employer did not provide any measures to prevent heatstroke.

The government's three-tier heat warning system - ranging from amber to red and then to the highest level black - advises employers to take necessary measures to prevent workers from getting heatstroke if the warnings are triggered.