Can air-conditioning in a bedroom save your life?

Written by Cool Angus on . Posted in Blog, Fire talk, Software

Research has shown (see 1 and 2 below) that, unlike sound and light, smell does not wake people up. The opposite tends to happen, with smoke having a soporific effect on already sleeping people. Therefore in the event of a fire developing and in the absence of any other sensory signal people will simply fall into a deeper sleep as the smoke enters the room and slowly poisons them. This is of concern to everyone, of course, but particularly to parents with young children.

The National Institute of Standards and Technology (NIST), a United States federal technology agency have developed and maintain the Fire Dynamic Simulator software that allows the modelling of fire and smoke simulations using computational fluid dynamic principles. I have used this software to examine whether the presence and use of an air-conditioning unit in a bedroom has any affect on the spread of smoke;

  • Does the air-conditioning slow down the entry of smoke into a bedroom?
  • And if so, by how much?

In particular I was interested to determine whether, or not, the use of an air-conditioning unit provides any meaningful benefit to sleeping individuals in terms of additional time before the smoke from a fire overcomes them.

It was noted in researching this topic that whilst there has been a good body of research papers carried out on the affect of forced ventilation in commercial environments, there appears to have been little, or none, done for residential dwellings and I was unable to find anything covering the effect of air-conditioning in the sleeping environment.


The model used was of a simplified home, with two otherwise identical bedrooms.

The Model

Although a simplified model, the aim was to reflect the proportions of a real home, so the dimensions used were based upon an average of some real life samples looked at on an Australian property website. It was necessary to use a ceiling height of 3.2m as this dimension works well in the the Fire Dynamic Simulator software for computational purposes. The ‘normal’ ceiling height of the residential dwellings looked at varied, and whilst generous, it was felt that 3.2 m was not unreasonable.

Floor areas modelled:

  • Main living area where the fire occurs of 69.76m2
  • Two identical (apart from air-conditioning) bedrooms each of 16.77 m2
  • A bathroom (door open) and communal hall between the two bedrooms


For the purposes of the simulation the ambient temperature in the house was set at 26º C, which whilst warm is not an uncommon night time temperature in the southern hemisphere during the summer months. The temperature of the simulated air-conditioning unit was set to input air into the room at a constant temperature of 20º C, some 6º C below ambient and maintain it at that level.

As it was not possible to change the ambient starting temperature in just one room, using the fire dynamic simulator software, it was deemed preferable to start the simulation running for a short period of time before the fire itself started. That way the room containing the air conditioning was allowed to get down to a lower temperature, before the fire started, thereby simulating a fire starting some time after the residents have gone to bed. This was set so the fire started at 150 seconds (2½ minutes).

We calculated the air flow one could realistically expect from an air-conditioning unit, based upon a random sample of commercially available residential units for sale, and used an average flow rate of 1.25 m/s for our air-conditioning vent.

The fire surface in the model was set to polyurethane as this is a material in common use in modern housing, which after comprehensive comparative experimentation by NIST has been shown to produce compartment fire results in the Fire Dynamic Simulator as close to a real fire as possible. Polyurethane foam is often used, in the form of flexible polyurethane foam (PUF), in furniture construction such as sofas and chairs and is also a common constituent in adhesives and paints used in homes.


It was expected that at the point when the fire started, having an air-conditioning unit in the bedroom, would result in that room having both;

  • a lower temperature than the ambient temperature in the rest of the property, and
  • as the door was fully closed, albeit with a gap at the bottom, there would be a natural resistance to the buoyant smoke being able to enter the room


The questions we set out to answer were whether the above expectations were born out and and if so what effect this had on the spread of smoke into that room. The assumption being that the slightly lower ambient temperature in the air-conditioned bedroom plus the positive inflow velocity would hold back the ingress of smoke, but to what extent?

Using the the Fire Dynamic Simulator software, it would appear that having an operating air conditioning unit in a bedroom (with the door closed) does indeed slow down the ingress of smoke into the bedroom and (in this simulation) by some considerable time, nearly ten minutes. If corroborated by further more extensive simulation and/or experimentation this knowledge could be valuable for fire safety in the home.

Note: The above is a much shortened excerpt of the full research conducted. If you would like the full research paper please contact me.


1. Nocturnal Olfactory Response To Smoke Odor
BY: J. L. Lynch – Irondale Fire and Rescue Service Irondale, Alabama
2. Scents will not rouse us from slumber, says new Brown University study
Kristen Cole – The News Service, 38 Brown Street / Box R, Providence RI 02912

Net Neutrality Wins!

Written by Cool Angus on . Posted in Blog

Good news if you believe in a free and open Internet!

Tom Wheeler the Chairman of the Federal Communications Commission (FCC) in the United States announced yesterday that, “I am submitting to my colleagues the strongest open internet protections ever proposed by the FCC, these enforceable, bright-line rules will ban paid prioritization, and the blocking and throttling of lawful content and services.”

In the US Internet access (broadband) is dominated by a few powerful companies, such as A&T, Verizon and Comcast. These Internet Service Providers (ISPs) had wanted to introduce a dual tier Internet service, where they could charge more for faster access. Their argument being that large content providers such as Netflix use disproportinate amount of bandwith and should therfore pay more.

Not unreasonable you may feel…. However, the worry for net neutrality advocates was that this was just the first step in what could prove a slippery slope and the end result would have been an Internet where only the wealthy would benefit from the faster services.

How does this affect the UK, if at all? Difficult to say as we have a more open and competitive service in this country. But, you can bet that if this had gone ahead in the US, our own ISPs would have been keen to see if they could also introduce a similar system to the UK. At least that is what I (and I’m sure others) feared.

It isn’t over yet, as the American ISPs are a rich and powerful group, who will not go down without a fight, but it is at least a step in the right direction!

Extinguishers in the home

Written by Cool Angus on . Posted in Blog, Fire talk

Do you have a fire extinguisher in your home? If not, why not?

This is a story from the Safelincs website:

“Last night I was sitting working at the kitchen table, when I heard a ‘fizz’ sound followed by a ‘pop’ – almost like the sound of a small balloon popping. I continued working, thinking that it must have been one of my daughter’s toys. But my mind was still trying to decipher the sound that I’d heard… I thought it was particularly strange because I’d heard the ‘fizz’ before the ‘pop’ - whereas if a balloon had burst or something similar, it would usually be the other way around!”

“Eventually my curiosity got the better of me and I had to go and see what had made this strange sound. Well, thank goodness I went to look, because what I found was yellow flames coming from underneath our electric night storage heater. Fortunately my brain switched into ‘crisis mode’ and I quickly moved anything flammable away from the storage heater, and switched off the electricity supply to that heater.”

“I then dashed to the cupboard in our kitchen where we store our 1kg powder fire extinguisher and fire blanket. While racing back to the fire, I pulled the pin out of the extinguisher, and then I took aim and blasted powder at the fire. Within three blasts from the extinguisher the fire had completely gone out! My wife and daughter came rushing through to see what all the commotion was about, and I explained what had happened.”

“It was shocking how quickly the fire spread, and I was so grateful that I knew exactly where the extinguisher was and how to use it without thinking!”

“This experience really caused us to re-think our fire protection — especially with a young child in the house. Within hours I’d re-located all our extinguishers to make sure they were easily accessible from key locations around the home. And I made sure that my wife also knew exactly how to use the extinguishers so that she could also react quickly in the event of a fire.”

“It really was a terrifying ordeal, but as a result we have become much more diligent about extinguisher locations and making sure that we are all fully familiar with how to use each type of extinguisher — and the types of fire on which they can be used.”

This is just one of many similar stories about real people in real situations and how being able to tackle the fire quickly and safely saved them from what could have become a major catastrophe.

What do you need?
The room with the greatest risk of fire is usually the kitchen, simply because it tends to have several sources of ignition such as the cooker, hob and electrical appliances. The kitchen is also well stocked with materials that burn relatively easily; fats, oils, tea-towels and wooden cupboards. But, it is not the only room where there are risks. Any room containing electrical goods can be at risk (as the above story illustrates). Behind the television in many living rooms is often a rat’s nest of wiring and multiple sockets.

A versatile fire extinguisher for the home is the Dry Powder fire extinguisher, although care must be taken to avoid breathing in the powder itself during use. These can be used on electrical fires, wood, paper, textiles, etc as well as flammable liquid and gaseous fires. You don’t need a hulking great fire extinguisher spoiling the decor in your home either, as they are available in smaller sizes, such as 1kg or 2kg, for under £15.

In addition to a fire extinguisher we would recommend a fire blanket for the kitchen as this can sometimes be easier to use and more effective on a pan fire. These can be found for around £10.

How many do you need? That will depend on the size and layout of your home of course, but even if you start with just the one fire extinguisher and fire blanket in the kitchen, it is better than nothing at all. Many companies sell kits such as this one for under £30 which include an extinguisher, fire blanket and smoke detector.

Once you have the equipment make sure that everyone, of a suitable age, is aware of where they are located and how to use them in an emergency. It may not be possible to actually ‘set-off’ the extinguisher, as it would then need servicing, but get everyone to handle it so they can feel the weight, see where the controls are located and be shown how they should direct it at a fire.

Teach the acronym PASS:
Pull the pin out of the fire extinguisher, so it is ready for use
Aim at the base of the fire (not at the flames)
Squeeze the top handle or lever
Sweep from side to side until the fire is extinguished

Of course you should only tackle a fire if it is safe to do so. If in doubt, it is better to get yourself and everyone else out of the home, and then call 999.

For comprehensive fire safety information, including professional Fire Risk Assessments, visit the Safety Management (UK) website or telephone +44 (0)1524 784356

Will you wake up if there is a fire?

Written by Cool Angus on . Posted in Blog, Fire talk

Do you need smoke alarms in your home? Or, can you rely upon your own senses to alert you to the dangers of a fire? It is a good question and not one with an easy answer…

There has been some research into this, but not as much as you might expect. One issue researchers have to contend with as far as fires go is that they are not able to test with ‘real’ smoke, as it is a poisonous cocktail that kills people! So they can only use a simulated smoke smell.

Research carried out on behalf of the Irondale Fire and Rescue Service in 1997 found that of the ten subjects tested only two of them woke up. Research by Brown University in 2004 concluded, “While sound can disrupt sleep, scents cannot. People cannot rely on their sense of smell to awaken them to the danger of fire…” Rachel Herz, a professor of psychiatry at Brown University, believes strongly that people do not have a sense of smell whilst sleeping. “You cannot smell while you are asleep,” she says. “You don’t smell the coffee and wake up; rather you wake up and then smell the coffee.”

Why is this important?

The chances are that if a fire starts in your home, the smoke from the fire will reach family member’s bedrooms much sooner than the actual flames and if you are sleeping the chances are you will not wake up. Smoke can contain, in various proportions; carbon monoxide, hydrogen cyanide, hydrogen sulphide, ammonia, hydrogen chloride and others.

These chemicals interfere with the supply of oxygen to the body, cause disorientation, swelling of the delicate lining of the airways and can numb your senses resulting in a deeper sleep rather than waking up. And of course death!

What to do?

Having established that you are unlikely to be woken up by the smell of smoke, make sure you have working and regularly tested fire alarms located in the right places in your home. If they are not mains powered, change the batteries every year as a matter of course. Fire alarms do not last forever and, as they are fairly cheap to buy these days, change them for new ones if they are over ten years old.

Have a plan for the whole family, so everyone knows what to do if they hear a smoke alarm sounding. Worried about your children thinking you are a boring old so and so? Who cares? You may just save their lives one day!

If there is a fire, get out of the house as soon as possible and stay out.

Desk – Blogging Tool

Written by Cool Angus on . Posted in Blog, Software

Desk – Blogging Tool

New, and really rather good, text editor. Desk (available on the App Store for a few pence over £20).

Like others of the same ilk it allows you to concentrate on the text only, removing all other distractions from the screen, until they are needed.

What I like are the simple things it does so well.

  • It had a Day and Night (or light and dark) mode which is easily toggled. I like the Night mode, even during the day, which is light text on a dark background, as I find this less distracting.
  • Nothing but the text appears on the screen until you move the cursor. Then a narrow toolbar appears on the right of the screen with a few publishing options. A character and word count appear at the foot of the screen.
  • Whilst Desk supports Markdown, it also you to use keyboard shortcuts and/or when some text is selected a small pop-up dialog appears above the text with some formatting options.

One of the main features is the way it connects and interacts with blogging software, such as WordPress. Once setup it makes writing a blog post very easy and straightforward. For instance this article was written and published to my blog within a few minutes (you don’t say…). Adding and manipulating images is straightforward. Just drag and drop into the article then drag to where you want it, resize using corner handles if required.