It began developing a device in response to a government appeal for firms to take part in a national effort to increase the number of ventilators.
But in a note to staff, founder Sir James Dyson said that demand for ventilators had been less than first envisaged.
The Cabinet Office said that tests on ventilators are still ongoing.
Dyson's ventilator has been undergoing clinical tests in recent days and the government had previously said it intended to order 10,000 machines.
But Sir James told his staff that only a quarter of those available were currently being used.
As a result, he said, the government did not need to acquire as many of them.