Many ventilation systems on the market today use the roofspace as their source of ventilation air.

The conditions in the roofspace are ideal for incubating mould and fungi.

  • Always dark

  • Warmed and dried from sunshine

  • Topped up with dampness every night  

An independent Building Inspector in the US, (from where NZ has adopted its ventilation standards), has compiled a web page on the affects of mould in homes he has inspected. We recommend you visit this site: 

Mould and fungi in the home is not a new phenomenon, the dangers were well known in biblical times.  The following is an extract from a letter we received from Dr T J Sprott (OBE), the noted NZ Forensic Scientist:


Cot Death Study: Poisoning Hypothesis

There is a very intriguing passage in Leviticus Ch 14, part 2, wherein the Jewish people were given certain instructions regarding their houses if they found on the inside walls a mildew (or in some versions referred to as a spreading leprosy or a plague). It clearly refers to a fungal growth and describes the colour as greenish or reddish. This is the colour of the fungus, which we now call Scopulariopsis brevicaulis, which has the capacity to convert any compounds of phosphorus, arsenic and antimony into very poisonous gases. The description of the “mildew” varies a little depending upon the version of the Bible which one consults.

In brief, the priest was instructed to scrape off the mildew and examine it again after seven days. If the growth ceased the people could return to the house, but otherwise the house had to be destroyed and taken out of the city to be disposed of in an unclean place. It all seems strange but there must be a logical explanation.

My speculation is this: The mortar used in those days by all the tribes of the region and later by the Romans was what we call “pozzolana”, a natural cement. The pozzolana was derived from volcanic regions, and such earths frequently contain arsenic. The growth of this mildew could therefore have generated arsine, with deadly results especially for children.

The common moulds are of the Aspergillus variety, “niger” (black in colour) and less frequently “flavus” (yellow). To me it is significant that there is no warning against these, which is reasonable since are harmless and do not convert the elements P, As and Sb to the tri-hydrides. Only S. brevicaulis and a few related types do so and these are all coloured as described.

Does this mean that the Jewish people knew of the danger of these moulds? It seems the only explanation. If so, this must surely be the earliest reference to the phenomenon which later manifested itself in:

the 1880s with thousands of child deaths, a problem finally solved in 1892 by the Italian chemist Gosio as being produced by the same fungus from arsenical pigments in wallpaper, curtains, carpets &c.

the fatal poisoning of some children in UK in 1932, from arsine generated by S.brevicaulis from building blocks made with clinker containing arsenic

the near-fatal poisoning of Mrs Clare Booth Luce in Rome, 1947, from arsine derived from copper arsenate pigmented paint on the ceiling of her bedroom

and again from the 1960s to the present day as SIDS, when babies became exposed to compounds of the elements in question, added to their cot mattress for various purposes. The wool of some sheepskins also contains arsenic and phosphorus

Leviticus is, of course, a series of laws or instructions designed to protect the health, cultural and religious integrity of the Jewish people. It seems that the passage was a health-related matter.

Dr Sprott’s book “The Cot Death Cover Up?” contains important information related to the subject of Indoor Air Quality.

Some Mould and Fungi are as dangerous to human health as asbestos or hazardous Volatile Organic Compounds.

In the Christchurch Press, page 2, July 22 2000, was a report about hospital in Whangarei, where a dead rat infested with maggots was in a roofspace. This caused the operating theatre to be closed for two days.

If you think that this is absolutely disgusting, think on this ……… how many rats, mice, birds or smaller creatures like spiders, flies, wasps, dust mites, feather mites and spider mites will die and decompose in your roofspace over the next 5 to 10 years ? Have you ever actually inspected your own roofspace to see how clean it is ?

A dead rat is usually identified by smell or can be seen, but there are just as many mould and fungi spores, and other allergens that become airborne from the natural composting of hundreds, thousands or millions of other minute and unseen creatures that inhabit the living and roofspaces of most NZ homes.

Fungi perform the natural process of breaking down, rotting and composting dead matter. While this is a natural process, the danger to humans is often overlooked

Consumer protection laws requires Health Warning Labels on Compost and Manure packaging — This is quoted directly from a bag of common Potting Mix …

“CUSTOMER INFORMATION — This mixture contains living organisms which may cause illness and allergies in humans. Keep moist, and avoid direct inhalation”.

In 1995, 5 people died in Christchurch after inhaling fungi allergens from garden compost.

If there are spider webs in your roof space, there must be a regular food source to feed them. Spider droppings are every bit as foul as cow or horse droppings, except that they are smaller, the same composting that occurs with horse manure occurs with spider droppings. The same mould and fungi and spores become airborne and are available to be ingested by occupants of your home.

It is just plain common sense to ensure that roofspace air IS NOT used as ventilation air and that air from roofspaces, filtered or otherwise, is never introduced into your living space. (Outdoor air is also specified as ventilation air in the NZ Building Regulations).


0800 DRY AIR  (0800 379 247) 


Products are New Zealand made by Avon Electric Ltd.


Avon Electric Ltd
25 Taurus Place, Bromley
P.O Box 19748, Christchurch 8030 
Ph: 03 381-5595  - Fax: 03 381-5596