Philips issued a voluntary recall for millions of its sleep apnea machines and life-sustaining ventilators after it found that foam used in the breathing devices may degrade into particles and be ingested or inhaled by users, according to a release by AARP.

The foam may also give off chemical emissions. Exposure to foam particles or emissions is potentially toxic, the manufacturer said, and may cause cancer, among other health risks.

The recall involves an estimated 3 million to 4 million Continuous Positive Airway Pressure (CPAP) devices globally, based on the company's production and shipment data. Over half of the devices were sold in the United States, with the majority of them being the first-generation DreamStation products. DreamStation 2 products are not affected by the recall.

Philips has not received reports of deaths, but it is aware of consumers finding black debris within the air-path tube and feeling sick.

Potential risks from exposure to the foam include headache, irritation, inflammation, respiratory issues and possible toxic and carcinogenic effects. Risks from chemical exposure include headaches, irritation, hypersensitivity, nausea/vomiting and possible toxic and carcinogenic effects.

The company hasn't received reports about patient exposure to chemical emissions.