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Effect Of Duration On Infection Probabllity
Posted: Sun Dec 19, 2021 5:20 pm
by Stranger Mouse
I know that the old 2 meters / fifteen minutes guideline didn’t guarantee safety and that it pretty much got blown out the water anyway with delta let alone omicron. I’m just wondering if anyone has any ideas on what would be a good guideline (for personal use) on time duration *probably* being safeish if someone were to, for instance, sit next to you on a train.
Not looking for solid figures but wondered if I was being over cautious be being concerned over 5 or 10 minutes before I can take evasive action
Re: Effect Of Duration On Infection Probabllity
Posted: Mon Dec 20, 2021 1:10 am
by Herainestold
Stranger Mouse wrote: ↑Sun Dec 19, 2021 5:20 pm
I know that the old 2 meters / fifteen minutes guideline didn’t guarantee safety and that it pretty much got blown out the water anyway with delta let alone omicron. I’m just wondering if anyone has any ideas on what would be a good guideline (for personal use) on time duration *probably* being safeish if someone were to, for instance, sit next to you on a train.
Not looking for solid figures but wondered if I was being over cautious be being concerned over 5 or 10 minutes before I can take evasive action
Fifteen minutes was before Omicron, it has to be less now. It also depends on your face covering.
This (old) chart shows 15 minutes if unmasked, 30 mins for a medical mask and 2.5 hours for a N95 (FP3) mask.
If we can assume that the relative times are reasonable then if it was 5 minutes unmasked, it should be half an hour or so if are wearing a FP3. I am guessing that a properly fitted FP3 should give you enough time for a bus or tube trip. Maybe.
My fear is that Omicron is so infectious a few seconds exposure may be enough.
https://1lnfej4c7wie44voctzq1r57-wpengi ... e-Mask.pdf
Re: Effect Of Duration On Infection Probabllity
Posted: Mon Dec 20, 2021 4:38 pm
by jimbob
Herainestold wrote: ↑Mon Dec 20, 2021 1:10 am
Stranger Mouse wrote: ↑Sun Dec 19, 2021 5:20 pm
I know that the old 2 meters / fifteen minutes guideline didn’t guarantee safety and that it pretty much got blown out the water anyway with delta let alone omicron. I’m just wondering if anyone has any ideas on what would be a good guideline (for personal use) on time duration *probably* being safeish if someone were to, for instance, sit next to you on a train.
Not looking for solid figures but wondered if I was being over cautious be being concerned over 5 or 10 minutes before I can take evasive action
Fifteen minutes was before Omicron, it has to be less now. It also depends on your face covering.
This (old) chart shows 15 minutes if unmasked, 30 mins for a medical mask and 2.5 hours for a N95 (FP3) mask.
If we can assume that the relative times are reasonable then if it was 5 minutes unmasked, it should be half an hour or so if are wearing a FP3. I am guessing that a properly fitted FP3 should give you enough time for a bus or tube trip. Maybe.
My fear is that Omicron is so infectious a few seconds exposure may be enough.
https://1lnfej4c7wie44voctzq1r57-wpengi ... e-Mask.pdf
That chart looks a bit too symmetrical.
From personal experience, when I wear a FFP2 mask, it's far easier to get a good fit on the inhalation than exhalation.
And with a cloth mask, I'd suspect there is more benefit to the source wearing it than the receiver.
Re: Effect Of Duration On Infection Probabllity
Posted: Wed Dec 22, 2021 9:13 pm
by Stranger Mouse
Just a thought but can you actually put a cloth mask over an FFP2 or will that make it impossible to breathe? I’ve been told by some people they are surprised I can managed the double masking I currently do but I just forced my way through it.
Re: Effect Of Duration On Infection Probabllity
Posted: Thu Dec 23, 2021 10:56 am
by WFJ
Stranger Mouse wrote: ↑Wed Dec 22, 2021 9:13 pm
Just a thought but can you actually put a cloth mask over an FFP2 or will that make it impossible to breathe? I’ve been told by some people they are surprised I can managed the double masking I currently do but I just forced my way through it.
Cloth masks do not stop virus particle, and any benefit to putting one over a medical mask comes from keeping the medical mask closer to the skin. FFP2 masks are designed to form a seal with your face. Putting a cloth mask over the top is at best useless and possibly harmful if it pushes against the mask and causes it to break the seal with your face.
If you want the FFP2 mask to be as effective as possible, do not reuse masks, keep your face clean shaven and bend the metal strip around your nose properly, so you can feel the seal on your face and see the mask move inwards as you breathe in.
Re: Effect Of Duration On Infection Probabllity
Posted: Thu Dec 23, 2021 8:16 pm
by Stranger Mouse
WFJ wrote: ↑Thu Dec 23, 2021 10:56 am
Stranger Mouse wrote: ↑Wed Dec 22, 2021 9:13 pm
Just a thought but can you actually put a cloth mask over an FFP2 or will that make it impossible to breathe? I’ve been told by some people they are surprised I can managed the double masking I currently do but I just forced my way through it.
Cloth masks do not stop virus particle, and any benefit to putting one over a medical mask comes from keeping the medical mask closer to the skin. FFP2 masks are designed to form a seal with your face. Putting a cloth mask over the top is at best useless and possibly harmful if it pushes against the mask and causes it to break the seal with your face.
If you want the FFP2 mask to be as effective as possible, do not reuse masks, keep your face clean shaven and bend the metal strip around your nose properly, so you can feel the seal on your face and see the mask move inwards as you breathe in.
Thanks for that. I’ve noticed from the double masking that the main thing the top mask does is provide a better seal.
There’s part of me which things about just giving up on the extra precautions anyway since no other f.cker even does the basic stuff
Re: Effect Of Duration On Infection Probabllity
Posted: Thu Dec 23, 2021 9:15 pm
by discovolante
Obviously this is very much a layperson perspective. But I'm not sure you can really put even that much of a rough estimate for this kind of thing. I get that you're asking about minutes vs seconds etc but surely it's going to depend on lots of factors - viral load, mask/type of mask/no mask, ventilation, length of time since vaccination etc...just not sure it's something you can mathematically calculate as you go about your day to day interactions. Which probably isn't very reassuring but hey...
Re: Effect Of Duration On Infection Probabllity
Posted: Thu Dec 23, 2021 10:28 pm
by Herainestold
WFJ wrote: ↑Thu Dec 23, 2021 10:56 am
Stranger Mouse wrote: ↑Wed Dec 22, 2021 9:13 pm
Just a thought but can you actually put a cloth mask over an FFP2 or will that make it impossible to breathe? I’ve been told by some people they are surprised I can managed the double masking I currently do but I just forced my way through it.
Cloth masks do not stop virus particle, and any benefit to putting one over a medical mask comes from keeping the medical mask closer to the skin. FFP2 masks are designed to form a seal with your face. Putting a cloth mask over the top is at best useless and possibly harmful if it pushes against the mask and causes it to break the seal with your face.
If you want the FFP2 mask to be as effective as possible, do not reuse masks, keep your face clean shaven and bend the metal strip around your nose properly, so you can feel the seal on your face and see the mask move inwards as you breathe in.
Good info, thanks.
I have been using a new medical mask under a tight fitting three layer cloth mask, I will switch to FP2 when I get some.
Re: Effect Of Duration On Infection Probabllity
Posted: Fri Dec 24, 2021 12:31 am
by WFJ
discovolante wrote: ↑Thu Dec 23, 2021 9:15 pm
Obviously this is very much a layperson perspective. But I'm not sure you can really put even that much of a rough estimate for this kind of thing. I get that you're asking about minutes vs seconds etc but surely it's going to depend on lots of factors - viral load, mask/type of mask/no mask, ventilation, length of time since vaccination etc...just not sure it's something you can mathematically calculate as you go about your day to day interactions. Which probably isn't very reassuring but hey...
Also a lay person perspective, but I completely agree with this. Any estimates of "minutes of protection" are going to be massively effected by real world factors that make such estimates almost worthless. From what I understand, I think the best way of looking at it is:
cloth mask - no protection for wearer - negligible protection for others
medical mask - negligible protection for wearer - some protection for others
FFP2 mask - reasonable protection for wearer and others
cloth over medical - a bit better than medical alone, but still a long way behind FFP2
Re: Effect Of Duration On Infection Probabllity
Posted: Fri Dec 24, 2021 9:32 am
by Sciolus
Sure, but in the real world, we need some way of evaluating how much risk we're at and how much we're prepared to take. I might have a budget of 100 risk points per week. A 20-minute trip to the supermarket is 5 risk points, except none of the other twunts are masked so call it 8. Getting the train into the office is another 8, then spending the day with coworkers is 5. Seeing friends with schoolkids indoors is 50. Have I got enough points left to go out for lunch in a cafe on Saturday?
We can only guess what the actual numbers should be, but we might as well make intelligent guesses.
Re: Effect Of Duration On Infection Probabllity
Posted: Fri Dec 24, 2021 11:18 am
by discovolante
Sciolus wrote: ↑Fri Dec 24, 2021 9:32 am
Sure, but in the real world, we need some way of evaluating how much risk we're at and how much we're prepared to take. I might have a budget of 100 risk points per week. A 20-minute trip to the supermarket is 5 risk points, except none of the other twunts are masked so call it 8. Getting the train into the office is another 8, then spending the day with coworkers is 5. Seeing friends with schoolkids indoors is 50. Have I got enough points left to go out for lunch in a cafe on Saturday?
We can only guess what the actual numbers should be, but we might as well make intelligent guesses.
How is that real world? You're not more or less likely to catch it today based on what you did yesterday.
Re: Effect Of Duration On Infection Probabllity
Posted: Fri Dec 24, 2021 2:06 pm
by Bird on a Fire
I can see people doing some kind of mental arithmetic along the lines of "one quite risky thing vs two sightly risky things" or whatever. I'm not sure it's worth trying to quantify it to any great degree of accuracy.
Given the impossibility of knowing where and when you got it (especially omi), the cumulative risk over a few days or a week seems a useful unit to think about. I am more likely to get it this week if I go to a pub garden twice rather than once, for instance.
Re: Effect Of Duration On Infection Probabllity
Posted: Fri Dec 24, 2021 2:32 pm
by discovolante
Bird on a Fire wrote: ↑Fri Dec 24, 2021 2:06 pm
I can see people doing some kind of mental arithmetic along the lines of "one quite risky thing vs two sightly risky things" or whatever. I'm not sure it's worth trying to quantify it to any great degree of accuracy.
Given the impossibility of knowing where and when you got it (especially omi), the cumulative risk over a few days or a week seems a useful unit to think about. I am more likely to get it this week if I go to a pub garden twice rather than once, for instance.
You are, but that's more about frequency of exposure than length or proximity etc which is what the OP was asking. Talking about 'risk budgets' seems to be more a way of psychologically coping with your choices rather than figuring out how likely you are to catch it at any on point. And I'm not entirely sure it's necessarily effective unless you have a high level of control over your comings and goings, and seeing as hardly anyone has that much control over a long term basis I'm not sure it's great as a long term measure either. But I am not a psychologist.
Re: Effect Of Duration On Infection Probabllity
Posted: Fri Dec 24, 2021 3:29 pm
by Bird on a Fire
Well, popping into a pub garden for 5 minutes would be less risk than staying 2 hours. Hugging and kissing people or sitting at close quarters would be more risk than chatting from opposite tables.
All of which are things largely under one's control.
I do tend to think in terms of frequency, duration and proximity, I think. But there's also an unknowable threshold effect - get too close to a carrier and you're instantly toast.
Re: Effect Of Duration On Infection Probabllity
Posted: Fri Dec 24, 2021 3:50 pm
by discovolante
True but going back to the OP. The example given was sitting next to someone on a train. From what I can gather from other posts the OP is trying to prevent catching covid and passing it onto their elderly mother, so I'm assuming isn't going to be popping into pubs or going round hugging and kissing people. And I don't think that's something you can assess in that level of detail as you go about your day to day business. I'm not suggesting there aren't certain factors that increase or decrease risk that are within your control, just that there are also factors that aren't, and also that the amount of info at your disposal at any one time isn't enough to really know how safe you are.
Re: Effect Of Duration On Infection Probabllity
Posted: Fri Dec 24, 2021 4:52 pm
by Stranger Mouse
discovolante wrote: ↑Fri Dec 24, 2021 3:50 pm
True but going back to the OP. The example given was sitting next to someone on a train. From what I can gather from other posts the OP is trying to prevent catching covid and passing it onto their elderly mother, so I'm assuming isn't going to be popping into pubs or going round hugging and kissing people. And I don't think that's something you can assess in that level of detail as you go about your day to day business. I'm not suggesting there aren't certain factors that increase or decrease risk that are within your control, just that there are also factors that aren't, and also that the amount of info at your disposal at any one time isn't enough to really know how safe you are.
Can confirm I am not popping into pubs
Re: Effect Of Duration On Infection Probabllity
Posted: Fri Dec 24, 2021 5:03 pm
by Bird on a Fire
Stranger Mouse wrote: ↑Fri Dec 24, 2021 4:52 pm
discovolante wrote: ↑Fri Dec 24, 2021 3:50 pm
True but going back to the OP. The example given was sitting next to someone on a train. From what I can gather from other posts the OP is trying to prevent catching covid and passing it onto their elderly mother, so I'm assuming isn't going to be popping into pubs or going round hugging and kissing people. And I don't think that's something you can assess in that level of detail as you go about your day to day business. I'm not suggesting there aren't certain factors that increase or decrease risk that are within your control, just that there are also factors that aren't, and also that the amount of info at your disposal at any one time isn't enough to really know how safe you are.
Can confirm I am not popping into pubs
Fair dos, and sorry for my musings which weren't very relevant to your case.
I don't think it's possible to micromanage risk over a 5-10 minute timescale to be honest - it does sound like you're doing everything plausible
Re: Effect Of Duration On Infection Probabllity
Posted: Fri Dec 24, 2021 5:17 pm
by Herainestold
On some level it has to be riskier to sit next to somebody on the bus for an hour than for five minutes. It is impossible to quantify in a meaningful way.
I have limited myself to two shopping excursions per week, when the shops first open and are not crowded. Other than that, no contacts with people.
Re: Effect Of Duration On Infection Probabllity
Posted: Fri Dec 24, 2021 10:50 pm
by sTeamTraen
discovolante wrote: ↑Fri Dec 24, 2021 3:50 pm
True but going back to the OP. The example given was sitting next to someone on a train. From what I can gather from other posts the OP is trying to prevent catching covid and passing it onto their elderly mother, so I'm assuming isn't going to be popping into pubs or going round hugging and kissing people. And I don't think that's something you can assess in that level of detail as you go about your day to day business. I'm not suggesting there aren't certain factors that increase or decrease risk that are within your control, just that there are also factors that aren't, and also that the amount of info at your disposal at any one time isn't enough to really know how safe you are.
All of this.
Plus, still on the "limited info" bit: The biggest determinant of your risk is whether the person sitting next to you is infected (presumably still asymptomatically) or not. So probably the biggest difference you could make if you had good information about infection status is to choose whom to sit next to. But since we typically don't have that information, that could very quickly get into some possibly unjustified assumptions ("I don't like the look of that person, they seem like the kind who might have spent all of last night at a no-pass illegal rave").
Re: Effect Of Duration On Infection Probabllity
Posted: Sat Dec 25, 2021 1:21 am
by Millennie Al
Herainestold wrote: ↑Fri Dec 24, 2021 5:17 pm
On some level it has to be riskier to sit next to somebody on the bus for an hour than for five minutes.
Not necesssarily. For example, if you were guarantee to catch it in such circumstances within three minutes if they were infectious, then there would be no sigificant difference between five minutes and an hour. But we just don't know what is actually required to catch it. It is probably a complex interaction between the amount of virus someone is shedding, the way they are acting (e.g. are they breathing straight at you or in another direction), air circulation patterns, your susceptability, and any barriers between them and you.