Question about CRT mercury toxic - Page 1
Forum section: electronics / general

author: dozeyehabi
author_rank: Newbie
timestamp: March 31, 2019, 12:34:32 pm
content: Hi.My friend broke a oscilloscope several years ago, and he just put that in his bedroom, he have lived with that thing for several years until I warned him. I've heard that there's mercury in CRTs and they will escape as gas if broken, so how bad will that influence him, especially the nerve system?Thanks.

author: NiHaoMike
author_rank: Super Contributor
timestamp: March 31, 2019, 12:42:35 pm
content: It's CCFLs (not CRTs) that have mercury, but the amount is small enough to not be a problem in ordinary conditions.

author: daqq
author_rank: Super Contributor
timestamp: March 31, 2019, 12:43:25 pm
content: I have never known CRTs to have mercury inside of them. True there are tubes that do have some quantity of mercury (among other the common household flourescent lamp), but not CRTs.QuoteIt's very important for a CRT to have as little gas inside of them as possible.

author: TheWelly888
author_rank: Frequent Contributor
timestamp: March 31, 2019, 12:46:47 pm
content: I spilled some metallic mercury on my bedroom carpet when I was dismantling something about 20 odd years ago.It did me no harm!{twitch}

author: Halcyon
author_rank: Unknown
timestamp: March 31, 2019, 12:47:58 pm
content: Elemental Mercury has a boiling point of over 350°C. At normal atmospheric temperatures, it's usually in the form of a liquid. Mercury in CRT monitors is in the form of an amalgam. It's not until it enters the environment or is ingested that it becomes a hazard. No gas is released from a broken CRT either, inside is a vacuum. Any breach actually causes air to enter the cavity, not the other way around.Simply being in the same room as a cracked CRT poses no risk apart from a possible tripping hazard.

author: Ian.M
author_rank: Super Contributor
timestamp: March 31, 2019, 12:51:42 pm
content: CRTs don't contain any significant quantity of mercury as they use an electron gun to excite the phosphor. Its fluorescent tubes and lamp that contain mercury as they use UV from a low pressure mercury arc discharge to excite the phosphor to produce visible light.There would be negligible mercury vapour remaining from a single broken fluorescent tube in an adequately ventilated room a year later, and one-off exposure would have an insignificant effect on adults. However repeated or high level exposure is hazardous, and any mercury vapour (or other heavy metal) exposure is an undesirable risk for pregnant women, infants and children.N.B. the phosphor itself is usually toxic. Its normally bonded to the inside of the glass of the CRT faceplate or fluorescent tube or lamp but if you break it some may cone loose. Avoid breathing or otherwise ingesting the dust and *DON"T* cut yourself on the glass fragments . . . .

author: Ian.M
author_rank: Super Contributor
timestamp: March 31, 2019, 01:02:15 pm
content: Quote from: Halcyon on March 31, 2019, 12:47:58 pmDo you have a cite for that?Mercury in CRTs other than as trace inorganic salts in the glass seems to be a myth due to rampant Californication. It does contaminate the phosphors and glass of fluorescent lamps and tubes - not unexpected when they've been subjected to mercury ion bombardment at elevated temperatures for an extended period. Seehttps://core.ac.uk/download/pdf/61417932.pdfThe only reference I can quickly find to the use of amalgam in lamps or CRTs ishttp://www.dafp.de/wp-content/uploads/2015/10/The-analysis-of-modern-low-pressure-amalgam-characteristics.pdfand a quick skim indicates the use of amalgam is important for maintaining long term stability of the mercury vapour pressure. This wouldn't be a concern in a CRT where its desirable to maintain as hard a vacuum as possible.

author: dmills
author_rank: Super Contributor
timestamp: March 31, 2019, 04:22:35 pm
content: Just as long as nothing tacks a couple of methyl groups onto the mercury atoms....Metallic mercury is actually not all that hazardous, high boiling point and low bio availability, the issues come with its tendency to form organo-mercury salts if given half a chance, some of which are beyond nasty. There is a reason the NMR crowd dropped dimethy mercury as a useful agent.The fear of Hg has always struck me as a bit weird, rather like the panics over small amounts of tritium in the environment, lots of panicking but I can think of more important things to worry about.Regards, Dan.

author: German_EE
author_rank: Super Contributor
timestamp: March 31, 2019, 04:59:56 pm
content: I also played with mercury as a kid which makes this story kinda sad:https://www.inmaricopa.com/2nd-mercury-spill-puts-students-in-quarantine/The second incident was a broken thermometer

author: dmills
author_rank: Super Contributor
timestamp: March 31, 2019, 05:32:23 pm
content: I have no real idea where on earth Maricopa is, but just from that level of over reaction it almost has to be in California?Yep, played with mercury drop maze toys as a kid, also used a few hundred grams to make a simple homopolar motor Faraday style for a school science demo, didn't get any push back either.Regards, Dan.

author: ejeffrey
author_rank: Super Contributor
timestamp: March 31, 2019, 05:39:50 pm
content: Quote from: dmills on March 31, 2019, 04:22:35 pmThe problem with metallic mercury is that when it escapes into the environment it can easily turn into methyl mercury. When talking about typical small quantities this is a localized hazard: if a mercury spill that is not cleaned up properly gets into a damp basement or soil can react to produce methyl mercury which is a hazard. Mercury discharged into waste streams that ends up in lakes and oceans likewise can convert and is a widespread environmental toxin, but in the normal small quantities of a broken thermometer or CRL are dwarfed by coal burning emissions which *are* a serious environmental health hazard. This is largely because environmental regulations have really limited the amount of metallic mercury in everyday devices so that the total disposed of amount is relatively small. If we were as mercury happy as the 19th century that would be another story.Anyway, my guess is that the OP is confused between mercury and lead. CRTs AFAIK don't contain significant quantities of mercury in any form. However, they are made with leaded glass to shield against x-rays and actually contain a staggering quantity of lead. But a piece of leaded glass sitting on the shelf is still no danger. The problem is that water (especially acidic water) can leach the lead out and even small quantities of lead are dangerous especially to children as it is incorporated into their growing bones.

author: dmills
author_rank: Super Contributor
timestamp: March 31, 2019, 05:56:53 pm
content: Yea, but the lead thing is another slightly odd one.I mean, yea, toxic heavy metal (they more or less all are), but absent lead paint on the nursery walls and tetra ethyl lead in the petrol there is just not a lot of the stuff around any more, again I can think of other things to sweat.Even old lead pipes are not that big an issue providing the water is not too acidic (See the issues in Flint).Large scale coal burning is a lovely one, toxic heavy metals, including mercury AND a mess of radioactives, and the plants are dangerous to work in (As in workers die on a semi regular basis from industrial accidents) give me a few GW of nuke for a neighbour **any** day of the week!Regards, Dan.

author: Ian.M
author_rank: Super Contributor
timestamp: March 31, 2019, 06:16:33 pm
content: Quote from: German_EE on March 31, 2019, 04:59:56 pmAny competent school lab tech should know how to safely clean up a small mercury spill. Its quite simple - here's the EPA's instructions:https://www.epa.gov/mercury/what-do-if-mercury-thermometer-breaksGetting the kids out of the room immediately was the right thing to do, but the total exposure risk could have been minimised by immediate cleanup with flowers of Sulphur, rather than waiting for a Hazmat team from a different city. All that should have been left for the Hazmat team to do would be check for residual contamination, remove the contaminated waste, and 24H later check if the levels were safe for the affected room (not the whole building) to be reopened.It looks like it was near Phoenix, Arizona. That's 150 miles east of the California border so the area affected by epidemic Californication is obviously spreading!

author: German_EE
author_rank: Super Contributor
timestamp: March 31, 2019, 07:05:27 pm
content: The instructions from the EPA seem sensible, and a small container of powdered sulphur kept to deal with spills like this seems like a good idea. Rather than evacuating the kids I would be tempted to show them what to do if a spill occurs, and at the same time teach them that most chemicals when handled correctly are not a substantial risk.The idea of the shaving cream is a good one, I would not have thought of that!

author: tooki
author_rank: Super Contributor
timestamp: April 03, 2019, 01:19:33 am
content: Quote from: dozeyehabi on March 31, 2019, 12:34:32 pmYou're definitely confusing CRTs with fluorescent lamps. CRTs arevacuum tubes, and mercury vapor inside would prevent them from working properly — they need a vacuum. Fluorescent lamps (both tubes and compact) use mercury vapor, but the amounts are small and for a single broken lamp, it's sufficient to air out the room for a few hours.

author: tooki
author_rank: Super Contributor
timestamp: April 03, 2019, 01:21:26 am
content: Quote from: German_EE on March 31, 2019, 04:59:56 pmI wouldn't even be surprised if they later determined that it wasn't even a mercury thermometer, but a galinstan one...

author: Ben321
author_rank: Frequent Contributor
timestamp: April 04, 2019, 10:57:25 pm
content: Quote from: dozeyehabi on March 31, 2019, 12:34:32 pmIt's actually lead, not mercury. And that's embedded in the glass itself (much like the leaded glass used in observation rooms at a nuclear power plant, that let them see into the reactor to monitor it for problems, without getting killed by radiation). This leaded glass is used in CRTs to block x-rays that are emitted when electrons strike the front of the tube.

author: chris_leyson
author_rank: Super Contributor
timestamp: April 05, 2019, 12:06:25 am
content: I think people that tell you that there is mercury in a CRT are confusing it with the flashed getter inside the CRT. The "getter", the bright silver area on the inside of the CRT neck, is a reactive metal that absorbs small amounts of trace gas after the tube has been evacuated and sealed. When the tube is sealed the getter is vaporised by induction heating. CRTs and most vacuum tubes use barium as a getter and it's perfectly safe.

author: lwatts666
author_rank: Unknown
timestamp: April 05, 2019, 04:00:45 am
content: I would be far more concerned about the vacuum leaking out of the broken CRT and lurking in some dark corner waiting to suck in some unsuspecting reporter writing some FUD piece about household dangers...

author: coppercone2
author_rank: Super Contributor
timestamp: April 05, 2019, 11:08:42 pm
content: it is fairly volatile and it will all have been evaporated by now. fi you spill mercury always keep it ventilated for a long time.

author: tooki
author_rank: Super Contributor
timestamp: April 06, 2019, 10:20:14 am
content: Quote from: coppercone2 on April 05, 2019, 11:08:42 pmThere. Is. No. Mercury. In. A. CRT.

author: soldar
author_rank: Super Contributor
timestamp: April 06, 2019, 11:07:34 am
content: I don't know if this might have been said already but there is no mercury in a CRT and he may have been thinking of CFLs.

author: Ian.M
author_rank: Super Contributor
timestamp: April 06, 2019, 11:43:24 am
content: The Californication fiction of mercury in CRTs is probably due to mercury in early flat panel LCDs. Not in the LCD itself, but in the CCFL backlight tubes. Add in moronic bureaucrats and you get one size fits all legislation that doesn't distinguish between types of display or recognise that only early backlit LCDs (pre LED) contain any mercury.