Disclosure: I work with MENRED, an HVAC ventilation manufacturer. I’m sharing a practical ERV selection checklist for discussion; the linked article is company-affiliated.

A high heat-recovery rating can be useful, but it does not tell you how much energy the building will save over a year. The result also depends on the unit’s airflow and pressure conditions, leakage, fan power, climate, controls, maintenance and the HVAC equipment.

When reviewing an ERV proposal, I’d check:

• What does the rating measure: sensible, latent or total recovery?
• What test standard and operating conditions were used?
• Is the figure gross or net, and is leakage performance available?
• What fan power and pressure drop apply at the design airflow and external static pressure?
• How will supply and exhaust airflows be balanced after installation?
• Does the energy comparison include the fans, frost protection and affected HVAC equipment?
• Are bypass, defrost and filter maintenance appropriate for the project?

The comparison should keep the required ventilation rate and indoor air quality target consistent. Otherwise, apparent savings could come from providing less ventilation.

For engineers, designers and commissioning teams: which data point is most often missing from ERV proposals?

Full checklist:
https://www.menred-hvac.com/newsdetail/erv-efficiency-vs-real-energy-savings-what-buyers-should-check

Exhaust does not stop changing when it leaves an engine. Reactions in the atmosphere can produce new particles and alter the chemistry of existing ones. In laboratory experiments, aircraft-combustor emissions became substantially more reactive as researchers simulated days of exposure to atmospheric oxidants.

Their oxidative potential per unit particle mass increased six- to sevenfold after aging equivalent to approximately 12 days. Emissions from a marine diesel engine showed a different pattern in the same chemical test. The contrast suggests that freshly emitted exhaust alone cannot describe how particle reactivity develops in the air.

The study, published in Environmental Science Atmospheres, was led by Markus Kalberer’s group at the University of Basel. Alexandre Barth and Battist Utinger were its two first authors. The work examined chemical indicators associated with potential harm, rather than measuring disease or demonstrating a corresponding increase in human toxicity.

City council has long sought to dismantle the citizens idling complaint program and allow idling again in the city for the sake of big business. Intro 561-A is their latest attempt. Please sign the petition and tell Speaker Menin that NYC deserves clean air!

Hi everyone! I'm a grade 12 highschool student in Canada working on an independent research project regarding air quality and how it affects health. As part of my project, I'm hoping to learn from people who live in different countries and communities that have experiences or knowledge on air pollution. If you live in an area where air pollution is a noticeable issue, I'd love to hear:

- What is air pollution like where you live?
- Is air pollution something people around you are concerned about, or is it mostly overlooked?
- Do you notice air pollution affecting the health of your community?

Thank you for reading :)

Any recommendations for decent CO2 detectors that don't require Home Assistant or similar?

Anyone knows the PSI and PM2.5 in Riau Islands (Bintan)?

I recently bit the bullet and dropped over $600 on the View Plus Duo. My house is built partially underground and has multiple gas fireplaces so I am looking for radon and CO2 monitoring. I had a disappointing customer service experience (more below if you want the details) and will be returning, and would rather purchase from a company with more reliable support, especially at this price point. Are there any other companies you’d recommend?

[The sensors arrived and while the shipping box was pristine with no evidence of mishandling during transit, the inside packages clearly had been opened/used and returned. The sensors were grungy and covered in smudges and residue, the power cords were unraveled and haphazardly shoved back into boxes, and the boxes inside were already ripped open with significant damage. I reached out immediately with photos and requested a replacement or a partial refund to reflect the “open box” status and they refuse to do anything until receiving them back and are insisting that it was the mail carriers fault and they never would’ve shipped them like that.]

The sky looks like someone put a grey filter over the whole island. PM2.5 is nearly 300 µg/m³, which is well into hazardous territory.

My throat is already feeling off. Stay safe and mask up, everyone.

Hey there! I am just a bored Singaporean student that has personally felt that the latest shift in government message to 24h PSI and 1h PM2.5 has unintentionally deflated the raw numbers we have been observing daily, and has also just been a bit disorienting for those of us that grew up with our old 3h PSI numbers throughout the mid 2010s haze period.

Thus, I just made a small project that does the following:

1. Bring back the 3h PSI as an indicator that can be viewed (using the old 3h PSI formula based off on PM2.5 concentration)
2. Adding a 1h PSI indicator (which converts the 1h PM2.5 into our PSI scale, as I feel the PM2.5 scale is frankly quite confusing with weird bandings)
3. Draws directly from the NEA API which allows it to be updated quicker than the official NEA haze site.
4. Has a not-so-fun conversion of our haze into equivalent cigarettes :(

I would love to get more feedback on possible functionalities, and to see how it can be more helpful

Link: https://haze-tracker.pages.dev/

Hey everyone!

I'm planning to buy my first air purifier, but a bit confused by all the options available. There are so many brands, filter types, room coverage claims, and features that it's difficult to figure out what actually matters.

Since many of you already own air purifiers, I would love to hear your recommendations based on your real-world experience.

• Which air purifier are you currently using, and how has your experience been?
• What features should I prioritise when buying my first one?
• How important are CADR, HEPA filtration, and room size?
• If you were buying your first air purifier today, which one would you choose and why?

My wife has pretty bad allergies and our house is older. I keep seeing ads for air duct cleaning but I'm not sure if it's legit or just a scam. Does it actually help with allergies and air quality? We change our filters regularly but I'm wondering if we need to do more. Anyone here had it done and noticed a real difference? We're in North Jersey if that matters have tried to research a bit and found Welduct. Please help me if you have tried it :)

https://www.reddit.com/r/textosaleatoriedades/s/E4SgPto0uI

Is it caused by the No data point?

I’m a product builder exploring how people compare AQI readings with what they see, smell, or feel. Which sources do you trust, and what information feels missing?

I've only just considered CO2 levels in my bedroom being an issue.

Day 2, and it looks like 3 of us sleeping in the room brings it from 1000 to 1500 within 4 hours.

Our AC IS always on, opening a window to flush in clean air isn't a feasible plan as it would need to be performed multiple times a night.

We have split type AC so there is no filter option on that.

We have an old hole where a window type AC was which is currently boarded off with plywood.

I dont mind spending a reasonable amount up front, but the solution has to be quiet and not too expensive ongoing.

The bedroom gets no light into it.

The room is about 450cm x 450cm.

Potential solutions im thinking of (without really checking the products exist or what the recommended solutions would be) are

- A cheap duct fan system like a bathroom extraction fan but in reverse, maybe 3 speed so I can jack it up and open the door for the occasional full flush.

- In conjunction with the above, maybe cut a little extraction one way flow valve at the bottom of my door. Its the opposite side of the room from the hole and the bed is between them so that would create an air flow through the room and CO2 is heavier so shluld be pushed out more tgrough the door.

(Note, they are both on the "far left" of the wall but are on opposite walls, so the "right side" of the room wont be great in comparison

- plants. But no light. Temperature in the room will range from 25°c to 32°c generally. Humidity - tropical country, based on the 2 days of readings 50-75%

Am I missing any better reasonable solutions?

Any specific advice on the above thoughts?

Thanks