Tamper-resistant receptacles (marked with TR, sometimes know as TRR) are designed to be safer than regular outlets by making it more difficult to insert foreign objects. That said, there are lots of examples of things that were supposed to be safer which turned out to be more dangerous (uk outlet covers, wing floaters, margarine, etc.).

I could imagine tamper-resistant being less safe if they encourage kids to use both hands to insert foreign objects (disabling GFCI) or parents to leave extension cords in permanently to accommodate damaged plugs (increasing fire risk). is there any evidence to suggest that they are, in fact, safer than standard receptacles in the real world?

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    I think you might be over-estimating 2-3 year old crowd. Trying to insert two things at the same time in two different holes is not intuitive and would frustrate the short attention span little ones. I can't find numbers on shocks for TRR outlets, but here are some interesting reads. esfi.org/resource/… ecatalog.hubbell-wiring.com/press/pdfs/HS128.pdf – UnhandledExcepSean Mar 11 '19 at 20:43
  • it's numbers i'm really after. i think these things are safe, but i'm not sure how safe. it seems there are only about a dozen child fatalities a year from electrocution and i'm wondering if trr's could bring that down to zero, or if i should also add additional protections such as outlet covers or gfi breakers. i'm told that the UK outlet design is virtually impervious to child injury (none since 1990?). clearly trr outlets aren't that good since your link indicates 11% of child injuries involved a plug, which trr's won't prevent. – james turner Mar 11 '19 at 20:46
  • Keep in mind those numbers are old, so they likely are all standard outlets. Again, I couldn't find numbers on TRR shock rates. There are locking outlet covers which would be the pinnacle of safety I think in the US. – UnhandledExcepSean Mar 11 '19 at 20:54
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    It's difficult to make something foolproof as fools are so ingenious... – Solar Mike Mar 12 '19 at 9:52
  • the flaps are so stiff they've caused me a few busted knuckles and plenty of headaches. – dandavis Mar 12 '19 at 17:25

TRR are required by the NEC as of 2008 and contain built in shutters that prevent the insertion of an object into a single hole at a time. I could say that its obvious that most kids are going to try to only insert a single sharp object into the outlet, but I don't have any study to back that up.

However, there is a widely cited research study done by the Biokinetics Research Laboratory of Temple University that shows how ineffective many of the plastic outlet covers are. This study was done way back in 1997, but these plasic covers haven't changed much over the years.

Outlet cover types

Study results

The main points here are that 100% of kids age 2-4 could pull of one of the types and almost half of 4 year olds could pull off all three designs in less than a minute.

Now, it's true that this doesn't directly answer your question with a study of TRR outlets, but it does show that "standard" child protection was not adequate. Since TRR's have a physical shutter inside and should then prevent a non-zero number of accidents, they are probably better than no cover or a cover that can be removed (or forgotten by an adult). This should help with your research if nothing else.

Additionally, this blog from Leviton states (without a citation... I know...) that:

TR receptacles have been mandated in hospital pediatric wards for over 20 years and have proven to effectively prevent electrical injuries.

How do they know? Well presumably because they design and sell the devices to hospitals, but some hard numbers would be good.

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    the fact that "they design and sell the devices" is exactly why i don't trust their safety assessment. – james turner Mar 13 '19 at 1:05
  • @jamesturner That’s fair. They are “industry experts”, but they also have the most to gain from people buying more expensive outlets. – JPhi1618 Mar 13 '19 at 2:09
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    "industry experts" also tend to be blinded by the trees. they know so much about how to make things safe that they tend to ignore simple statistics. in the age of big data, that's no longer good enough. in the words of winston churchill: “however beautiful the strategy, you should occasionally look at the results.” – james turner Mar 13 '19 at 15:45

Keep in mind that TR outlets are a relatively new requirement. A quick search shows 2008 in the NEC, which typically has some lag time for state adoption. Once adopted, the NEC has immediate effect on new homes and major renovations. But there are plenty of older houses - plenty of circuits are still without GFCI or AFCI or even grounded at all, because if it ain't broke, don't fix it. That being said, plenty of parents of small children will either retrofit TR outlets or, more commonly (since it is easier & cheaper) add outlet plugs when they have little kids crawling around. I did that ~ 20 years ago because it was clearly a really good idea. But those outlet plugs are long gone - as soon as I could consider myself safe because they were a real pain to use. On the other hand, I have one good TR installed as part of a kitchen renovation at that time (electrician put in GFCI, added more circuits, etc. to meet current requirements at the time, but TR wasn't one of them so the above counter receptacles are not TR) and it works great - though I have no idea if any of my kids ever tried to abuse it.

Now to some numbers. Well, not so easy. First report I found (from CPSC) seems to be (a) primarily about product (the P in CPSC) issues than about the built-in receptacles and (b) has low enough numbers that it is hard to draw any conclusions.

Aha! The Electrical Safety Foundation International (ESFI) has some interesting statistics for 1991 - 2001.

  • 24,000+ children under 10 years old were treated in emergency rooms for incidents related to electrical receptacles - about 7 children per day
  • 89% are under 6 years old
  • 50% are 2-3 years old, the highest-risk group

and the typical injuries are related to sticking hairpins, keys and other metal objects into a receptacle. But wait, you say, doesn't it take TWO items to cause a problem? No, it doesn't. All it takes is ONE item placed in the hot slot of a receptacle with nicely moist hands and a finger (or any other body part) touching ground, which can include the center screw on many receptacles, as well as metal parts of many appliances, and now you have a complete and dangerous circuit.

Given those kinds of statistics, even a small decrease in the problem will have a significant impact on health & safety. It will take a while, but over time it should make quite a difference. Keep in mind also that the alternative of outlet plugs, if they even worked, and they don't work so well, as noted in another answer, was simply never used by many people. In my personal experience, typical thoughtful modern parents would use them. But most of the grandparents - who love to have the little grandchildren come over for a visit - never had outlet covers. Plus they are a pain to use for adults.

Could TR receptacles be better than they currently are? Yes. Most of the recent (a.k.a. mass market now that everyone must have them in new construction) are not nearly as good as the kind I have in my kitchen. But they are better than nothing at all and, I would argue, generally much better than outlet plugs.

  • Notably, touching live to a ground is less dangerous because it is a ground fault that GFCI protection is intended to guard against. Touching live to neutral does not have any protection. This would be an argument for adding GFCI as well (noting false trip issues). – user71659 Mar 12 '19 at 0:59
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    @user71659 Agree that touching live to neutral would be the worst. But my hypothesis is that single item (hairpin, paper clip, key, etc.) is the most likely problem (and of course totally blocked by most TRR because they require both slots to be pushed at the exact same time and with significant pressure) and even in more recent construction there are plenty of rooms where GFCI is not required even though AFCI is required - e.g., bedrooms (where kids will often be unattended) and living rooms. – manassehkatz-Moving 2 Codidact Mar 12 '19 at 1:09
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    Even without touching ground a live wire will give you a startling buzz. Child might not be permanently hurt, but they're going to cry for a while. – JPhi1618 Mar 12 '19 at 14:35
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    @JPhi1618 not if they don't complete the circuit. I work on hot-side all the time. It just means your normal is hot, and anything grounded is now dangerous to you. At extremes, you're up in the bucket and you need to pass a guy wire up or down, you never never drape it, you coil it up first and then toss it through the air. – Harper - Reinstate Monica Mar 12 '19 at 18:02
  • @Harper, huh, ok. I've touched a residential hot accidentally before and got a buzz out of it. Perhaps I was touching more than I thought. It'd didn't hurt or burn - just a little buzz. – JPhi1618 Mar 12 '19 at 18:05

there has been a 9% decline in electrical outlet injuries in the 0-4 age group since trr's became mandated by nec in 2008. this is probably due to a confluence of various factors, but it does suggest that trr's are at least as safe as traditional outlets:

cpsc product code 4061 (electrical outlets and receptacles), ages 0-4
year range      national estimate   cases in sample
1998-2007       16,786              789
2008-2017       15,268              630

it's also worth noting that even after 2008 when the injury was significant enough to admit the patient to the hospital, then the individual case reports are generally prototypical of the scenarios trr's are designed to prevent. e.g. patient stuck hairpin into electrical outlet and received burns. fortunately between 2008-2017, there were only 12 hospital admissions (and no fatalities) so it's difficult to draw any statistically significant conclusions.

unfortunately, in the same timeframe, extension cord injuries have increased 51%. possibly due to people trying to circumvent sticky trr's, although there are probably dozens of other more plausible alternative explanations

cpsc product code 685 (extension cords), all ages
year range      national estimate   cases in sample
1998-2007       27,495                675
2008-2017       41,551              1,020

source: cpsc query builder: https://www.cpsc.gov/Research--Statistics/NEISS-Injury-Data

  • While this is good news, I am skeptical that the drop is entirely - or even "mostly" - due to TRR. The code requirement was in 2008. While there may have been some states requiring it earlier, I am sure many took their time even well after 2008. Plus this only affects new construction & renovations. I find it hard to believe that in only a couple of years more than 25% of housing had TRRs. I would guess the real adoption rate at a few % per year. My hunch is there are other factors going on or someone is having fun with statistics. – manassehkatz-Moving 2 Codidact Mar 13 '19 at 2:07
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    Sorry, nice try but no cigar. I just took a look, and this is the same report that I listed in my answer as First report I found (from CPSC) seems to be (a) primarily about product (the P in CPSC) issues than about the built-in receptacles and (b) has low enough numbers that it is hard to draw any conclusions. TRRs are primarily about small children (adults generally don't go sticking hairpins in electric receptacles) and Table 2 on page 5 shows <1-19 as an average of 5 per year. The details in Table 5 on page 8 show that this is about products (appliance, tools, etc.) not receptacles. – manassehkatz-Moving 2 Codidact Mar 13 '19 at 2:36
  • good catch. i switched to data from the cspc query builder that is specifically for injuries related to product code 4061. – james turner Mar 13 '19 at 17:10

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