Bathroom Ventilation

[Jerry Bruette]

Has anyone heard of using positive pressure for ventilation in a bathroom?

We had confined space training at work last week and the instructor talked about ventilating a space with a bad atmosphere. He said to use positive pressure because it works better than negative. Then he asks if anyone has stayed in a hotel in California, claims that positive pressure is used for exhausting bathrooms and the mirrors never fog up. He also said that this is the way it's done in Europe too.

Anyone ever heard of this?

[Doug Garson]

No, but do you really want the odours from the bathroom pushed into the rest of the house?

[Wayne Lomman]

It's news to me in my part of the world. I'm with Doug and can't think why you would want to risk odours through the house.

I also challenge the assertion that positive pressure is better for clearing a toxic atmosphere. Positive pressure will leak gas wherever there is a gap leading to pockets of gas in uncontrolled locations. Much better to use negative where you control the exhaust along with correct inputs fresh air. Or so my confined space rescue training says. Cheers

[Jason Roehl]

I would think that you could use positive pressure with a non-powered vent to provide a place for the air to easily escape.

[Jim Becker]

I would think that you could use positive pressure with a non-powered vent to provide a place for the air to easily escape.

Exactly. The positive pressure into the space is balanced by providing passive venting out of the space.

[Matt Day]

Jason and Jim - your saying to pressurize the room/rooms adjacent to the bathroom, right?

If this is a master bath in question, What if the bedroom door is left open to the hallway? If it’s a 1/2 bath off the kitchen or living room, there are a lot of places to provide positive pressure for this to work.

A hotel room would likely work because there are exactly two rooms and the supply is always on in the bedroom.

All the building designs I’ve worked on (mainly commercial/healthcare) provide exhaust ductwork in the bathrooms, which we’d refer to as fart fans. Otherwise the supply and exhaust was balanced to provide the design cfm. OR’s and labs were positive pressure to keep them sterile.

[Yonak Hawkins]

..Sounds like an interesting idea, especially employing the passive outlet idea. Doors would have to be, somehow, sealed. How is this pressure created ?

[Matt Day]

Positive pressure is created by an air handler of some type, forcing air into the space. Such as a whole house air handler, or a room specific unit like th ones below the window at a hotel.

[Mike Cutler]

Yes, but the "positive" pressure is part of the intake air handler on top of the building, so there is no recirc of air. It's outside filtered air.
In the case of a confined space, the positive displacement of the air is part of the engineered aspect of a confined space entry permit. Generally you are looking at high velocity, high CFM fans that are really, really, loud.
If the air cannot be displaced, it needs to be educted, like a bathroom vent fan, and that is pulling a negative on the space which in turn will be displaced by the now positive atmospheric pressure from the surrounding areas. If you can't accomplish either, it's time for SCBA's.

A quality bathroom fan is all you need. They work.

[Jim Becker]

Jason and Jim - your saying to pressurize the room/rooms adjacent to the bathroom, right?.

I took it to be pressurizing the bathroom, itself...and providing a passive vent to the outside. This means you are "pushing through" the air rather than "pulling through" the air like you would with a traditional fan-powered vent.

[Jerry Bruette]

Yes, but the "positive" pressure is part of the intake air handler on top of the building, so there is no recirc of air. It's outside filtered air.
In the case of a confined space, the positive displacement of the air is part of the engineered aspect of a confined space entry permit. Generally you are looking at high velocity, high CFM fans that are really, really, loud.
If the air cannot be displaced, it needs to be educted, like a bathroom vent fan, and that is pulling a negative on the space which in turn will be displaced by the now positive atmospheric pressure from the surrounding areas. If you can't accomplish either, it's time for SCBA's.

A quality bathroom fan is all you need. They work.

I pictured the bathroom being vented as you say possibly with a HRV dedicated to the bathroom. I certainly wouldn't want to create a positive pressure and passive exhaust in the winter in cold climates.

The instructor did mention that the fan used to vent a confined space would be about 1000 cfm and it would be loud in the space while it's being vented.

[Jason Roehl]

I took it to be pressurizing the bathroom, itself...and providing a passive vent to the outside. This means you are "pushing through" the air rather than "pulling through" the air like you would with a traditional fan-powered vent.

That's exactly what I was thinking.

As for it being loud, well, one should think of not only dealing with unpleasant odors in a bathroom, but unpleasant sounds, too...

[Pat Barry]

Where does all this positive pressure come from?

[Mike Cutler]

I pictured the bathroom being vented as you say possibly with a HRV dedicated to the bathroom. I certainly wouldn't want to create a positive pressure and passive exhaust in the winter in cold climates.

The instructor did mention that the fan used to vent a confined space would be about 1000 cfm and it would be loud in the space while it's being vented.

Oh yeah, they are really loud. Double hearing protection required, and your ears can still sometimes hurt from the pressure changes. The vibration of the air moving is felt throughout your entire body. It's pretty fatiguing actually.
I'd rather strap on a tank and mask, but OSHA doesn't let the risk mitigation strategy allow that.

I'd be careful with any positive pressure in a bathroom. The toilet weir is going to let you know when you have to much, and it will only take an inch or two.

[David Helm]

That's exactly what I was thinking.

As for it being loud, well, one should think of not only dealing with unpleasant odors in a bathroom, but unpleasant sounds, too...

athroom fans are for removing moisture, not odors.
B