The Hidden Danger of Cal-Hypo

[JoyfulNoise]

UPDATE: Second fire breaks out at Lonza chemical warehouse in Bradley County - WRCBtv.com | Chattanooga News, Weather Sports

While I certainly advocate the use of cal-hypo when it can be substituted for liquid chlorine, it is a good reminder to treat it carefully. Cal-hypo can come in several different concentrations (% available chlorine) with 74% often easily obtainable. The downside to cal-hypo is that it emits chlorine vapors even in dry form and those fumes can act as a source of oxidation which can cause fires if flammable substances are stored near it. There are plenty of documented reports of cal-hypo fires happening but we rarely hear about them. Of particular concern to me is that people will use cal-hypo but not use it appropriately and open themselves up to exposure. Most cal-hypo for retail consumer use is sold as 1-lb bags of dry powder (and the bags are perforated so that they can breathe/emit chlorine fumes). If you use cal-hypo, the correct way to use it is to use an entire package and not leave any opened but partially used packages lying around. Doing that is a recipe for disaster.

So, if you plan to use cal-hypo in your pool this season, please do so safely by following all labelled package instructions. Also, make sure you store any cal-hypo in a safe location where it can not easily get wet and keep it stored away from any flammable substances.

 

[Texas Splash]

Thanks Matt for the education.

 

[JamesW]

The dust is a big issue. If dust is allowed to get everywhere and it meets certain contaminants, it can start a fire.

 

[zea3]

Before I knew any better I used to keep it in a cabinet in my laundry room, right above my gas dryer. Its a wonder I didn't burn the house down!

 

[JoyfulNoise]

Before I knew any better I used to keep it in a cabinet in my laundry room, right above my gas dryer. Its a wonder I didn't burn the house down!

Originally known as “bleaching powder”, cal-hypo was a common chemical found in most laundry rooms as liquid bleach was too unstable and expensive. Powdered bleach was very common all the way up to 60’s & 70’s....

 

[zea3]

Originally known as “bleaching powder”, cal-hypo was a common chemical found in most laundry rooms as liquid bleach was too unstable and expensive. Powdered bleach was very common all the way up to 60’s & 70’s....

And up until about that time most people dried their clothes out on a clothes line. No little igniters to worry about.

 

[JoyfulNoise]

And up until about that time most people dried their clothes out on a clothes line. No little igniters to worry about.

There are days when I wish my HOA allowed clothes lines! It is so hot and dry here that I can often run my dryer on the Air-only mode and the clothes will dry just using the low humidity air...

 

[mknauss]

I brought that idea up in my household. Unfortunately the household unit that says I am not allowed to touch the laundry did not think much of the idea ---------------

 

[PoolguyinCT]

UPDATE: Second fire breaks out at Lonza chemical warehouse in Bradley County - WRCBtv.com | Chattanooga News, Weather Sports

While I certainly advocate the use of cal-hypo when it can be substituted for liquid chlorine, it is a good reminder to treat it carefully. Cal-hypo can come in several different concentrations (% available chlorine) with 74% often easily obtainable. The downside to cal-hypo is that it emits chlorine vapors even in dry form and those fumes can act as a source of oxidation which can cause fires if flammable substances are stored near it. There are plenty of documented reports of cal-hypo fires happening but we rarely hear about them. Of particular concern to me is that people will use cal-hypo but not use it appropriately and open themselves up to exposure. Most cal-hypo for retail consumer use is sold as 1-lb bags of dry powder (and the bags are perforated so that they can breathe/emit chlorine fumes). If you use cal-hypo, the correct way to use it is to use an entire package and not leave any opened but partially used packages lying around. Doing that is a recipe for disaster.

So, if you plan to use cal-hypo in your pool this season, please do so safely by following all labelled package instructions. Also, make sure you store any cal-hypo in a safe location where it can not easily get wet and keep it stored away from any flammable substances.

When I was a youngster, maybe 17 or so. I was driving a vehicle, a can of pvc primer fell off a shelf & landed in a box of cal hypo. Boom..

In retrospect, 100% fault on employer as zero chemical handling training was provided..

 

[JoyfulNoise]

When I was a youngster, maybe 17 or so. I was driving a vehicle, a can of pvc primer fell off a shelf & landed in a box of cal hypo. Boom..

In retrospect, 100% fault on employer as zero chemical handling training was provided..

Hmmmmm .... I have some PVC primer and the pool store is right down the street with shelves full of cal-hypo....might make a fun addition to the 4th of July festivities !!

(Assuming I can hear anything above all the yahoos firing off their hand guns...)

I have years of OSHA chemical safety training and will likely die a slow, horrible and painful death from all of the industrial chemicals I was exposed to (assuming some venomous creature doesn’t get me first), so I’m a bit OCD on the whole “store your chems correctly and wear your proper PPEs!!” thing

 

[PoolguyinCT]

It’s not ocd. My daily service van has cages separating incompatibles..

One rocket surgeon rear ending a misloaded vehicle & it’s showtime!

 

[JoyfulNoise]

It’s not ocd. My daily service van has cages separating incompatibles..

One rocket surgeon rear ending a misloaded vehicle & it’s showtime!

True but it would be one heck of ride!!

 

[JamesW]

MEK and calcium hypochlorite creates chloroform. So, you will just sleep through the whole thing.

 

[PoolguyinCT]

MEK and calcium hypochlorite creates chloroform. So, you will just sleep through the whole thing.

No ignition?? I clearly remember a can of primer spilled in a box of Sustain cal hypo..
do you think another catalyst was at play?

Like I said I was 17 & my first season working for the guy that built my parents pool.. & one pool he admits, he wishes he never sold...

 

[JamesW]

I'm not sure if it would ignite.

 

[JoyfulNoise]

It’s entirely possible it would ignite. Primer is flammable and the reaction of hypochlorite with it would be very exothermic. The heat would drive further solvent evaporation until the explosive limit was achieved (1.8% lower limit with air). The flashpoint is sufficiently low enough (22F) that ignition and continuous burning would be a given.

I’ll go grab some cal-hypo tomorrow and let you know how it works out....what color primer should I get?

 

[PoolguyinCT]

It’s entirely possible it would ignite. Primer is flammable and the reaction of hypochlorite with it would be very exothermic. The heat would drive further solvent evaporation until the explosive limit was achieved (1.8% lower limit with air). The flashpoint is sufficiently low enough (22F) that ignition and continuous burning would be a given.

I’ll go grab some cal-hypo tomorrow and let you know how it works out....what color primer should I get?

Purple if a municipal inspector is coming or clear for a fussy pool owner!!

 

[Rocket J Squirrel]

There are days when I wish my HOA allowed clothes lines! It is so hot and dry here that I can often run my dryer on the Air-only mode and the clothes will dry just using the low humidity air...

I’m glad my HOA can’t see in my back yard. We have a stand-alone pop-up clothes line thing. With close enough friends, we hang up our towels & swimsuits before entering the house.

 

[JamesW]

It's the auto-ignition temperature that determines if the MEK will ignite. The auto-ignition temperature is 941 degrees Fahrenheit or 505°C.

It might ignite but maybe not.

I found multiple references that say this:

Do not use any type of dry granular calcium hypochlorite as a disinfecting material for water purification in potable water piping systems.

The introduction of granules or pellets of calcium hypochlorite with PVC and CPVC solvent cements and primers (including their vapors) may result in a violent chemical reaction if a water solution is not used.

So, that indicates a reaction, but not exactly what type of reaction.

 

[CJadamec]

Dont forget about the considerable amount of acetone that's also in PVC primer.