Do EMF Blockers Work? What Regulators Say About Shields

Do EMF Blockers Work? The Short Answer

The FCC and FDA say phone shields and stickers generally do not work as advertised. In a press release from June 16, 2011, the FTC states that there is no scientific proof that so-called shields significantly reduce exposure from cell phone emissions. The FTC also reports that shields interfering with signal may cause a phone to draw more power and possibly emit more radiation.

The FCC states that these devices generally do not work as advertised. The FCC adds that they may increase RF absorption in the head by interfering with proper operation and forcing the phone to increase power to compensate. The FDA states that it does not regulate such products and considers claims for them to be bogus.

The FDA reports that these products generally do not work as advertised and may interfere with proper operation of the phone. At best, the FDA says, they are harmless. At worst, they might prevent your phone from finding signal when you most need to make a call. The FDA says the closer a device is to you, the more energy you absorb. The FDA also states that there is no established health benefit from reducing an individual's RF exposure from cell phones.

Blocker Categories at a Glance

The table lists six categories and what the agency pages reviewed say about each.

Why Phone Shields Can Raise Phone Power

A shield can raise the exposure it claims to cut. The FTC says products that block only part of the phone, such as the earpiece, are totally ineffective because the entire phone emits electromagnetic waves. The FTC explains that by interfering with the phone's signal, phony shields may cause it to draw even more power and possibly emit more radiation.

The FCC reports that shields may increase RF absorption in the head due to their potential to interfere with proper operation of the phone. A blocker that works on the radio wave also works on the signal you wanted.

The FDA states that these products generally do not work as advertised and may interfere with proper operation of the phone. The FDA adds that these claims are bogus. At best, the products are harmless. At worst, the FDA warns that they might prevent your phone from finding signal when you most need to make a call.

What Reduces Exposure: Distance and Signal

ARPANSA notes that exposure to RF EME reduces very rapidly with distance. The FDA states that the closer the device is to you, the more energy you will absorb.

The FDA lists these ways to place more distance between a phone and your head: speaker mode, headphones or earbuds. It says to avoid calls when the signal is weak, because the phone then boosts RF transmission power. The FDA also suggests texting instead of talking, but not while driving.

The FDA also says there is no established health benefit from reducing an individual's RF exposure from cell phones. For home networks, UKHSA sees no need for extra action on home Wi-Fi exposure.

EMF Meters: What They Measure and What They Miss

ARPANSA says a magnetic field (gauss) meter measures fields from electrical sources at frequencies from 25 Hz up to 1,000 Hz. These measurements are read in milligauss, where one milligauss equals 0.1 microtesla.

ARPANSA states that such a meter 'is not suitable for the measurement of radiofrequency fields emitted from telecommunications sources such as mobile phones, mobile phone towers, Wi-Fi, smart meters, etc.' Readings taken a few centimetres from portable electronic devices 'may be false'. The meter is suitable for powerlines, substations and electrical appliances such as a toaster or hair dryer.

None of the agency pages reviewed evaluates consumer radio-frequency meters, so no accuracy claim is made about them, either way.

Canopies, Paint and Pendants: The Evidence Gap

None of the agency pages reviewed tests sleep canopies, shielding paint, pendants or bracelets. A material that blocks radio waves also blocks the signal a phone or router needs.

NIST notes that high-frequency millimeter waves have a limited ability to penetrate obstacles. Because of this, a wall or window changes what reaches you.

How To Spend Your Attention Instead

The FDA suggests three specific habits:

• Use speaker mode, headphones, or earbuds to place more distance between your head and the cell phone.
• Avoid making calls when the signal is weak as this causes cell phones to boost RF transmission power.
• Consider texting instead of talking, but do not text while driving.

The FDA also states that there is no established health benefit from reducing an individual's RF exposure from cell phones. UKHSA sees no need for extra action on home Wi-Fi exposure.

One guide covers Wi-Fi radiation at home. Another covers EMF and sleep. A third covers 5G health effects and the HHS review.

What Would Change This Answer

An independent test of a shield category that shows lower measured exposure at the body without raising phone output would change this answer.

No agency evaluation found showing a shield lowers exposure without raising phone output.