Gmcdually

I am installing a ventilation system in a 30 x40 building which requires me to install four grill locations , which then goes to an inline blower to remove stale or dangerous gases formed while moving cars around . My opinion is I should install grill locations low verses high as gases are heaviest than air. Amy opionions would be helpful .

RROLDSX

Amy couldn't make it but I'll chime in. Barring any building code requirements, which I hope you've looked into, I would put them high. You also need to ventilate the shop for heat. Then I would use a shop floor fan for further ventilation and air movement. JMO.

Mike77

for garage exhaust the air should be drawn out from low to the ground. Make up air is need to replace the air you exhaust out

tinner

The grilles should be low. You should check local code's. Around here, I believe it is 24" or lower to the floor.

Gmcdually

Thanks for replys , I failed to mention the garage is climate controlled and really would just use system whike moving cars around from one point to another .

jaunty75

What gases?

The gas emitted when moving cars around that is dangerous is carbon monoxide. CO is slightly less dense than air at similar conditions. This, coupled with the fact that the exhaust gases, when initially emitted, will be quite a bit warmer than room temperature, means that the CO will rise. That's why we place CO detectors higher up, rather than lower down, in the room. Your vent grilles should be high up on the walls.

Gmcdually

Yes carbon monoxide is my main concern. My initial feeling was also to put high because the heating of the exhaust would help to make it rise , I am now thinking of putting two low and two high to cover bases Thanks again for input .

Mike77

They should be down low 2 feet off the floor. No question about it.

Mike77

Ever been to a race track on a cold November morning? Exhaust gas laying like fog in a field.

tinner

Check out the exhaust in a parking garage once. They are low.

Gmcdually

Thanks for replys , based on overall opinion I have decided to put all four exhaust vents low.

classicmuscle442

Not lower than two feet for snow.

Mike77

'For snow" ??? Hopefully he won't get too much snow INSIDE his garage.

Gmcdually

Unlikely I will get snow outside either here on coast rough in complete

zeeke

X2 Molecular weight of air is 29 and CO is 28.01, slightly lighter so it will move with air when there is a cross wind but rise slowly when air is stagnant this coupled with the temperature difference will determine how quickly it rises. You also need to make sure your local code and National Electrical Code doesn't require you to abide Class I, II or III locations. You can find that in NFPA 70 Chapter 5.

Gmcdually

So now I am thinking I need to move the air by installing a couple ceiling fans to force air back down to vents when in use. There is no requirement to install this ventilation in a residential environment according to inspector , but this is a personal choice for safety as there is living space above . Thoughts ?

RROLDSX

I still say the vents should be high. You can use the ceiling fans to draw the air up and out or push it down and out the doors and/or windows. If you close up the upper area of the shop the fumes and gases have no where to go. You can also use a large shop floor fan to clear everything out in a hurry. I may be wrong but the requirement for lower vents could be for farm animals and methane. I'd check with the experts if I were you. Good luck.

Koda

Unless you are going to be bringing engines to operating temp and tuning them with the doors of the building closed regularly, no vent other than a large shop fan out the door is needed. I spent most of my teenage years living above a garage in a 20x60 building, and the only side effects I noted was the occasional being woken up on a Saturday by the 70s Corvette directly below me.

My car plant uses downdraft systems at each pit on the vehicle performance lines, and there are people in the pits as well. Plant normal HVAC handles them at the end of the sales line, as well as air exchanges from opening the door.

Yellowstatue

Discuss the problem with your local Fire Dept. They would have the expertize.

RROLDSX

Great idea.

Gary M

I would ask the inspector that talked with you before. He is going to have the best info for you. He inspects all day every day.

zeeke

Let's start by saying you should have the system engineered by a professional. You are introducing life hazards with the tenants above. Reality is if someone dies everything you worked for is on the line, let alone the guilt you will have to live with.

Ok, now let's talk reality about CO.
Not only should you have CO detectors throughout the areas above but you should also have a monitoring system where you can physically read how much CO is present in the work area. For those of you that have worked in these conditions, Corporations don't care about workers safety they care about profits. Sorry but it's the cold truth. You are cutting corners on something that is much more serious than most people understand.

Now I'll explain the "nerd" aspect of the info in the picture. IDLH is Immediate Death or Life Hazard, so 1200 Parts Per Million will kill you. For those of you that are sceptical, never under-estimate how quick you can get to 1200 ppm. Remember, it's parts per million which converts to 0.12% of one million, not much at all. Oxygen is roughly 19% and to sustain life you need a minimum of 16.5%. that's 19,000 ppm.

TWA is Time Weighted Average, that's 50 ppm in an 8 hour work day as per OSHA regulation. And CO is cumulative, which means it will build up in your system.

CO is flammable at 12.5% (12,000 ppm).

Getting back to what was previously stated, the gases coming out of the exhaust systems will be hotter than the air even on a hot day which will cause the CO to rise rapidly and seep through all the cracks in the ceiling, settling in the upper floors. I have experienced this as a Haz Mat first responder more often than you would think, so it is reality. Now you have the facts not the opinions. I hope this helps with your decisions.

Gary M

Put in electric powered detectors too cause batteries suck.

Happy Trails

Sounds like you want this ventilation for moving cars around. You could use wheel dollies instead to move your cars around.

Couple style options just for reference:

I use something similar to move snowmobiles around, and they work very well.

Gmcdually

Wow , overwhelming responses , thanks to all . I do not plan on working on cars while inside building , I just thought that if I had to move a couple cars to get another out that it would be nice to have some extra venting . My plan was to open two garage doors and three windows , flip the four vents on , and turn on big shop fan , then move cars around and leave all running for 10 or 15 minutes after done and then close back up . I am installing C.O . Detectors upstairs and down even though the inspector said it was against code to install in garage as they expect some C.O. there and said they would be going off all the time . (True Story). I am installing anyway . While no one will be living above it is finished space that friends or relatives might use some . I really thought I was being overly cautious , but maybe not . I will check with the local fire dept for there recommendations , and report my findings . Again thanks to all for info .

zeeke

Running 1 car indoors for 10 minutes could put you over the 10,000 ppm range. It's one thing to move 1 car out of a garage, it's a totally different thing to have them running in an enclosed area. The more that is trapped in the environment the more it banks down towards the ground displacing O2. I agree with the inspector about putting CO detectors in the garage area, they are not designed to measure CO only to warn about small amounts of CO. Depending on which type, some will alarm as low as 0.5 ppm. In a short time you will burn out the sensors making them in effective, which in turn will give you a false sense of security. Also depending on the unit, they are only reliable for 5 to 10 years. That's why I suggested metering equipment in the garage area. At the very least you could obtain a personal meter like the one pictured. Not sure who makes this, possibly MSA. I'm back to work tomorrow night, I'll see if the others aren't worn like this one. This meter low alarms at 35ppm and goes into high alarm at 100ppm, Maxes out at 999 ppm. There are many different types you can choose from. CO is a serious issue to many people take lightly. When you pull bodies out you get a real sense of how dangerous it is. The math doesn't lie. I'm not asking to believe a cautious first responder, that is why I laid it out above, so you can see the info for yourself. Please don't dismiss this as an overreaction. By the time you realize you are overcome it's too late to help yourself. Yes it's that quick. Do some research on how CO doesn't allow O2 to enter your red blood cells, then you will get a better understanding on my concerns.

I can also go on about the long term effects of exposure to burning hydrocarbons and absorbing carcinogens but I won't bore you with those details. The IDLH is much more important. We all want to be around to enjoy the fruits of our labor, with the proper info and precaution we give ourselves a better chance.

I also agree hard wired battery backup detectors are the way to go upstairs if it's still possible.

D. Yaros

Do not know that it is a solution, or the perfect solution, but what I do is have a "good old fashioned back-in-the day exhaust port in my garage door and a heavy duty tailpipe hose that runs from the tailpipe to and through the exhaust port. Works for me?

jaunty75

It works if the car is not moved, but the OP wants to move cars around. Can't do that with a hose attached to the tailpipe.

cherokeepeople

if this is what you will be doing why do you need the ventilation??

Gmcdually

The cost to install system is low. I am being cautious and did not want to cut corners when it comes to safety , do I need this system ??. Not sure , but I am sure it will help. I am also going to incorporate some of the ideas posted here . Thanks to all