A question of ventilation

[KingAether]

I have read a bunch here, done some searches via google and found conflicting information on CO so i wanted to check so it can be a bit more specific to my work space. 
  I'm a day or two from finishing a 10x10 cinder block shed as a work space and getting started with the forge, while I'm very versed in fire safety and use I've just started to consider ventilation for CO. The shed has a corrugated roof without the foam filler ridges so 1-2cm gaps all along the front and back, a 1/2" gap under the door and the top 2/5 of the door can open separate to keep animals out and one window pane still missing.  I'm not to worried about the cold, the garden is fairy wind shielded and in the small space i have the forge will keep it warm.
 I plan on buying a monitor over the weekend and figuring that out but would like to not have it beep at me of course. Will the mentioned gaps and openings be enough once the last window is in or should i maybe put in slanted slats instead for a consistent, larger opening. 
  Also is CO(2) heavier than oxygen? isn't it? many conflicting posts about that, Considering drilling some holes in a bottom block each side of the shed for vents if it is but would really rather not put my drill or my arm through that job and curious if i should put the monitor at knee height or just chuck it on the bench
Thanks in advance for any advice and reading my rambling, im rather excited to start

[swedefiddle]

Good Morning King,

If you put your location in your Avatar, you may find someone who is close to you.

Talking to someone face to face trumps a keyboard any day. Your family probably doesn't want you to go to sleep!! Don't err on the side of thrifty, If you don't have GOOD VENTILATION, you have a Death Trap. Period!! Carbon Monoxide creeps up on you, you don't realize you have a problem. Good Night!!

Neil

[greenskpr]

10 hours ago, KingAether said:

Also is CO(2) heavier than oxygen? isn't it? many conflicting posts about that, Considering drilling some holes in a bottom block each side of the shed for vents if it is but would really rather not put my drill or my arm through that job and curious if i should put the monitor at knee height or just chuck it on the bench

The googles say otherwise wrt CO..  slightly lighter than 'air'.  My 0.02 is measure where you'll be instead of where you think 'it' might be if you're going to measure at all. So, put it at head level where you do most of your breathing.

As I figure the venting plan out for my own shop, I'm basing my exhaust fan needs off the room volume and targeting how much air I want replaced per minute while I'm doing any kind of welding, tig,mig,stick or forge with the doors closed.

This info here is helping me along those lines. 

[ThomasPowers]

CO exposure is a leaky bucket cumulative system.  It builds up and "leaks away" so you want the build up to be slower than the leak away!  Measuring it where you are breathing it is the way to go.  Don't forget it can migrate into attached structures too. 

I get some warning: I get the CO headaches---got one at a SOFA meeting once when a storm blew up and so they closed the sliding doors down most of the way.  That's in a pretty large open room too.  That's why my smithy is 20'x30'x10' with two 10'x10' roll up doors and open gables that add another 60 sq ft of venting.

[KingAether]

Thanks for the information and links.. Thankfully no attachments to worry about, its at the end of the garden along a large alleyway behind a supermarket. As it stands i can't afford to do anything fancy.. Or anything much at all right now. Ill keep an eye on the monitor and if needed ill get a fan to put on the floor. I remembered i have a "greenhouse" extraction unit and tubes somewhere in storage, can't remember if its specifically for heat or CO, but im running the light on an extension cable already so not sure about powering it  

[Irondragon Forge ClayWorks]

Greenhouse extraction units control heat by ventilation, exhausting hot air and bringing in cool air, sounds like it would work a treat to me.

[Latticino]

It all depends on the size of the unit.  You need to look at the airflow the greenhouse system induces when in operation (CFM) and compare that to the room volume and forge burner size you have.  Unfortunately ventilation codes have not kept up with the recent upswing in interest in blacksmithing, and provisions regarding venting the appliance (forge) are typically deferred to the manufacturer's requirements (which don't exist in any commercial or DIY builds I've seen).  The closest thing in the 2015 International Mechanical Code is for Educational Metal Shops, which require at least 10 CFM per person and 0.18 CFM per SF of floor area.  For your 10 x 10 shop that would be a minimum of 38 CFM of ventilation air.  In my opinion that is grossly insufficient for safe operation of a smithing shop with a gas forge.  I feel that you need to exhaust (and makeup) at least the products of combustion in addition to the occupant ventilation requirement.  At minimum I would target mechanical exhaust at 10 air exchanges per hour for your forge.  If your roof is at 15' for the 10 x 10 structure that would require at least 250 CFM of exhaust.

Personally I don't think sophisticated controls of the exhaust fan are required.  Turn it on when you start your forge and shut it off approximately 10 minutes after the forge is turned off.  Any other controls are just a potential point of system failure.  My personal system has a manual switch for the exhaust fan with an override to turn it on if the room temperature gets to a certain point (set currently at 85 deg. F.).

[Charles R. Stevens]

Solid fuel forges are easer to deal with as they are essentially fireplaces, and their for guidelines for them work well. It may help to think of a gas forge more as a comertial kitchen. 

Know as I know Latticino makes his living designing and  installing commercial ventilation systems I would take his recommendations very seriously.

if memory serves, CO sticks to hemoglobin 16 times better than O2, so ear on the side of cation.

[KingAether]

6 hours ago, Latticino said:

It all depends on the size of the unit.  

Its gonna take me a while of research to fully understand that, takes me a while on new things due to Aspergers but  thank you for the detailed explanation. What is a good example of 38~ CFM in terms of a general appliance ? Large fan, open window, etc? I brought a new drill bit today and drilled 3 x 5 holes in the wall in place of an air brick and plan on checking what exactly it is i have in storage, might have actually been a power unit, not extraction. 

[JHCC]

7 minutes ago, KingAether said:

takes me a while on new things due to Aspergers

Just FYI, we have a number of members here on the autism spectrum. It's a pretty ASD-friendly place.

[KingAether]

Thank you JHCC, appreciate knowing that! 

[Latticino]

I'm afraid you missed my point.  38 CFM is insufficient. A small toilet room fan will give you that much exhaust. You should strive to get 8 to 10 times that much, at least, if not much more.  

As for the opening for the fresh air, the size there depends on how strong an exhaust fan you have (external static pressure it can exert), what noise level from the system you can tolerate, and whether you have an issue with entrained weather (rain or snow). A good rule of thumb would be for entry velocities to be kept below 500 feet per minute.  I'm not sure what you mean by 3 x 5 holes.  3" x 5" square?  How many?

It is best to err on the side of caution.  In my shop I use a medium size sidewall exhaust fan that probably moves over 15,000 CFM and keep a full size door open when forging.  I also have a CO monitor.

[ThomasPowers]

Calculations are great *IF* you can be sure ALL details are taken in account, (was there a factor for altitude, outside wind blowing against the outlets/inlets,???)  Traditionally in engineering you make a calculation and then apply a safety factor and the more failure might impact people's lives the greater the factor used! The old joke was that pyramids were just tombstones with a large safety factor applied when they were built...

So a lot of smiths don't bother to be real precise with a calculation and just use a huge safety factor.  My shop has about 260 sq feet of open ventilation when in use. ( 2 10'x10' roll up doors and 2 20'x3' open gables each with 30' open space.) Even so I know that standing right in front of the forge I am probably picking up some CO just from location.

So when people ask if opening 1 window in their sealed garage will be enough ventilation; my crogglement is Olympic class!  (And yes we have had that exact question!)

[Latticino]

Thomas,

Agreed.  There is also a rather profound difference between "natural" (unpowered) ventilation, like you use, and mechanical ventilation (fan powered), like I use.  The chimney effect can also come into play.  In my shop, in addition to the 30" diameter sidewall exhaust fan (ideal for high airflow/low static pressure applications, think barn peak exhaust fans) I have a 10" turbine vent in the roof peak to take advantage of the buoyancy of the hot exhaust gasses.  When it comes to proper ventilation I'm a belt and suspenders guy.

[ThomasPowers]

I've been thinking of closing in the gables and using a large exhaust fan in one of them---like an attic fan.  I'd like to cut down on the snow/rain blowing into the shop... I don't close the doors until the anvils start blowing over---we get fairly intense winds up and down the valley and the doors are oriented to take advantage of that.

My Father used to say "Theory has killed more good men." when he wanted to impress on me that after theory comes experimentation and empirical results trump theoretical results.

(He also used to say that the NEC was a minimum not the best!)

So if I was building a fancy high $ shop I would hire someone like Latticino to design/install the ventilation system---and then would install CO detectors anyway!

[JHCC]

Latticino would have included the CO detectors in the original design. 

[bubba682]

I started looking at options for ventilation in my shop as well right now i'm using an 8'' sucker like we use at work with 50' of vent hose which i put above where im welding and forging area and vent ouside.So far the co2 monitors are silent but i want a permanent overhead exhaust eventually.Cost ,noise and airflow are my three factors so i'm lookin for something cheap,quite and will work in a 24' by 24' shop.

[Marc1]

Just to clarify what seems to be a recurrent mix up. 

CO2 is Carbon dioxide, formula is O=C=O. The only contribution of energy to our planet that is a closed system, an island if you want ... comes from the sun, and CO2 makes it possible to convert light into carbohydrates through the process of photosynthesis in green plants. Bottom line, without CO2 there would be no life on this planet. 

CO is carbon monoxide. Formula is one molecule of carbon and one molecule of oxygen linked by a triple link, ( not easy to type). This is a toxic gas, slightly lighter than air and that needs to be vented out of the room. The greeks used CO to execute prisoners. 

The confusion between carbon, carbon monoxide and carbon dioxide is easy to trace back to the latest eagerness to blame CO2 for about everything under the sun including baldness, and call it "carbon" . 

CO2 sensors are very useful in greenhouses where CO2 is artificially increased to increase yields. Also necessary in submarines and other enclosed spaces like tanks or caves to see if it is safe to enter. Submarines operate with CO2 up to 5000 ppm as opposed to 400 ppm in the atmosphere. Higher concentrations are not toxic but reduce the available oxygen. The atmosphere is 78% nitrogen, 21% oxygen, 0.9% argon, and 0.03% carbon dioxide. From that 0.03% of CO2 present in the atmosphere, humans produce 3.4%, so 0.000102%.

Carbon monoxide (CO) on the other hand is highly toxic, and kills by reducing the oxygen carrying capacity of blood ( it binds with hemoglobin) It is a very common cause of death and it's effects are cumulative. Very common in boats and very dangerous since there are no warning signs. concentrations as low as 30 ppm (part per million) can lead to problems including poor judgement. CO sensors are important and the location should be as stated before, at head level. A CO2 sensor would be useless in an ordinary workshop. 

Plenty of good information on Wiki and other sources. Please learn about CO2 and it's importance for life on the planet, and make sure you can distinguish CO2 ( the good ) from CO ( the bad ), and C (  the ugly ) that is solid and very useful for writing, heating and even forging if you are so inclined

[bubba682]

Lol my bad i put the 2 in by mistake anyway i am still looking for a system thats cheap quiet and has the ability to work in my little area.  Cheap being the important thing...

[ThomasPowers]

CO2  can kill you as well; but it's due to suffocation rather than the active attack of CO.  

[KingAether]

Thanks for all the information guys, been offline a little while but i have just read through everything and am taking it in. I tried to move things outside over the week but the set-up didnt work out so im back to trying for good ventilation. I got the extractor out of storage finally yesterday but have been told it might be unusuitable for my use to due how its built posing a risk of sparks and explosions but surely hitting the hot metal in and of itself could also cause a spark? this is what i have, any ideas? The label says it passes 187 m3/h

[Charles R. Stevens]

It would depend on shop size and how close to the heat source you place it. I wouldn’t use it in a chimney but to to move stale shop air out it should be safe enough.  

5000cf an hour would give a 10’x10’ shop about 5 changes an hour. 

[Frosty]

On 12/3/2019 at 12:58 PM, JHCC said:

Just FYI, we have a number of members here on the autism spectrum. It's a pretty ASD-friendly place.

There are also a number of us who survived serious TBIs Traumatic Brain Injuries and strokes. IFI is pretty easy on us folk living with cognitive issues. Make yourself to home, know any good jokes? 

The warning about spark and explosion hazard regarding that blower is for flammable gas leaks so as long as you never leave the tank valve open on the propane cylinder it's not an issue. Remember if you're going to use the forge turn the exhaust fan on before you open the tank valve or light the forge. 

Frosty The Lucky.

[Marc1]

19 hours ago, KingAether said:

Thanks for all the information guys, been offline a little while but i have just read through everything and am taking it in. I tried to move things outside over the week but the set-up didn't work out so i'm back to trying for good ventilation. I got the extractor out of storage finally yesterday but have been told it might be unsuitable for my use to due how its built posing a risk of sparks and explosions but surely hitting the hot metal in and of itself could also cause a spark? this is what i have, any ideas? The label says it passes 187 m3/h

 

That is a good axial fan to vent the workshop. Nothing wrong with it. For an explosion to occur you need a higher concentration of flammable gases. Surely if you enter the workshop and it smells badly of LPG or petrol or other solvents, you will not switch the fan on and rather open all windows doors and look for the source or leave no necessarily in that order

For everyday use, that is perfectly adequate, There are other fans, where the motor is not in the path of the air being moved. They are centrifugal and the motor can be totally enclosed and cooled by fins on the body rather than being open. Good for helping a flue or venting toxic or flammable gases, but a bit of overkill to vent a workshop. 

[KingAether]

Thank you all very much for the replies, taken a load of my mind for sure!